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Hi all, I want to build a dedicated power supply board mounted to the back of the case and remove the regulator that is currently on the raduino, I also want to try to "clean" as much noise as possible from the supply whilst doing this. I only have rudimentary knowledge of this stuff but the below is my attempt at designing something for this. The idea is to clean up the 12V supply before connecting it to the ubitx mainboard and also use a resistor to drop the voltage into the regulator somewhat before feeding that into the Raduino. I am not sure what value would be good for R2. I would be grateful for any suggestion as to how I could do this better.  Best regards, Peter.
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Peter,
Before you go through the trouble of building in the "noise" filter, I would first verify that the noise is coming from the 12 supply.? The best way to do that is to test the noise level on battery power.? You do not need to transmit, so any 12v battery capable of supplying 250 to 300 ma for a short time should do.? I have used a car jumper battery that I have and found little to no difference in the noise level on battery power vs mains supplied through either of my TexPower 13.8volt switching supplies. The noise is coming from the antenna in my neighborhood caused by QRM and high QRN noise levels on the air in general.
With the above understanding, I will make some suggestions for R2 to reduce the power dissipation of the 7805 regulator.? ?That does depend on the total current that you will need from the regulator, and THAT depends on what you have planned to add onto the rig that will need 5 volts.? If you add up the power requirements of all of the devices on the stock rigs, the total current is much less than 200ma, more like 120 ma (approximate, as I have not done all of the spec sheet validations? I did look up the stock version 6 2.8" display and that has a max of 80ma).? Then you have the minimum voltage that the 7805 needs to regulate to 5 volts.? I use 3 volts to get some safety margin.? That means you need to supply 5 + 3 = 8volts minimum at maximum current.? If the input voltage is truly 12 volts, and you want 8 volts to the regulator minimum at 200ma, and you need a 4volt drop at 200 ma, then 4/.2=20ohms.? That resistor will need to dissipate 4*0.2 = 0.8 watts.? All of these calculations are DC values, so the simple E=IR and P=EI and the transforms work.
For my rigs, I am adding second Nanos, larger displays with built-in GUI processors, and signal processors, so I have upped the max current to <1 amp (the maximum that the 7805 provided by HFSignals can regulate) and added other safety margins to get 4 ohms at 4 watts.? Were I to do it again, I would have added a second 7805 to supply the auxiliary equipment and not modified the Raduino board.
In general, the stock setup works well, and no changes are needed.? Adding a heatsink to the regulator can help if you are going to operate in high ambient temperatures.??
The other comment that I would make is that if you find you have RF noise from the power supply, then you will need to add capacitors to filter the higher frequency.? Something like a 0.1 to 0.01 uF ceramic disc.? The 470uF will not filter higher frequency stuff.? There is too high of internal resistance at RF in electrolytic capacitors.? You may also be better off to add an RF choke instead of the resistor.? I will let someone more knowledgable on that subject to make a true recommendation.
The above are my thoughts and should be verified before you take action on them.? I do make mistakes at times.
73
Evan
AC9TU
|
Hi,
I would agree that a noisy power supply should be tamed at the power supply. I will suggest looking at the schematics of PC switching power supplies and focus on the filtering circuits that introduce the AC supply current from your electric energy company - aka your power mains. There are capacitors and chokes in that filter. I had a problem with one a number of years ago and could not have that computer turned on while using the radio. That is really inconvenient when we want to run digital modes:)
I found those filter parts had been omitted to save a few pennies. The circuit board had the traces and the mounting points and the silk screen for the parts. It had jumpers to carry AC power past those places and no filter parts. I installed the needed parts and the computer was then usable with the radio.
I hope this helps somebody.
73,
Bill KU8H
bark less - wag more
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On 7/9/20 12:28 PM, Evan Hand wrote: Peter,
Before you go through the trouble of building in the "noise" filter, I would first verify that the noise is coming from the 12 supply.? The best way to do that is to test the noise level on battery power.? You do not need to transmit, so any 12v battery capable of supplying 250 to 300 ma for a short time should do.? I have used a car jumper battery that I have and found little to no difference in the noise level on battery power vs mains supplied through either of my TexPower 13.8volt switching supplies. The noise is coming from the antenna in my neighborhood caused by QRM and high QRN noise levels on the air in general.
With the above understanding, I will make some suggestions for R2 to reduce the power dissipation of the 7805 regulator.? ?That does depend on the total current that you will need from the regulator, and THAT depends on what you have planned to add onto the rig that will need 5 volts.? If you add up the power requirements of all of the devices on the stock rigs, the total current is much less than 200ma, more like 120 ma (approximate, as I have not done all of the spec sheet validations? I did look up the stock version 6 2.8" display and that has a max of 80ma).? Then you have the minimum voltage that the 7805 needs to regulate to 5 volts.? I use 3 volts to get some safety margin.? That means you need to supply 5 + 3 = 8volts minimum at maximum current.? If the input voltage is truly 12 volts, and you want 8 volts to the regulator minimum at 200ma, and you need a 4volt drop at 200 ma, then 4/.2=20ohms.? That resistor will need to dissipate 4*0.2 = 0.8 watts. All of these calculations are DC values, so the simple E=IR and P=EI and the transforms work.
For my rigs, I am adding second Nanos, larger displays with built-in GUI processors, and signal processors, so I have upped the max current to <1 amp (the maximum that the 7805 provided by HFSignals can regulate) and added other safety margins to get 4 ohms at 4 watts.? Were I to do it again, I would have added a second 7805 to supply the auxiliary equipment and not modified the Raduino board.
In general, the stock setup works well, and no changes are needed. Adding a heatsink to the regulator can help if you are going to operate in high ambient temperatures.
The other comment that I would make is that if you find you have RF noise from the power supply, then you will need to add capacitors to filter the higher frequency.? Something like a 0.1 to 0.01 uF ceramic disc.? The 470uF will not filter higher frequency stuff.? There is too high of internal resistance at RF in electrolytic capacitors.? You may also be better off to add an RF choke instead of the resistor.? I will let someone more knowledgable on that subject to make a true recommendation.
The above are my thoughts and should be verified before you take action on them.? I do make mistakes at times.
73
Evan
AC9TU
|
It's definitely coming from the mains, if I switch off the soldering iron I get a <clack> on the audio of the radio, if I switch off the main light switch in the room I get an extremely loud <CLACK>. I have a PS30SWII switching power supply, I was considering doing this on its mains lead..
... which looks encouraging, but I also want to "filter" more on the incoming 12v. I also have the problem of "clicks" when using the encoder and you can hear "noise" when pressing the touch screen.
More info is that I will install a Nextion 5" screen at the weekend along with a second nano. I have some info on how to reduce the noise from the Nextion.
Evan, thanks for the info on calculating the required resistor size, that all makes sense as does the comment about the disc capacitor.
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The ¡®clacks¡¯ are most likely radiated noise and not conducted. This is normal. ? Dale W4OP ?
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From: [email protected] [mailto:[email protected]] On Behalf Of peter.mccracken@...
Sent: Thursday, July 9, 2020 1:09 PM
To: [email protected]
Subject: Re: [BITX20] Building a 12V Supply Board ? It's definitely coming from the mains, if I switch off the soldering iron I get a <clack> on the audio of the radio, if I switch off the main light switch in the room I get an extremely loud <CLACK>. I have a PS30SWII switching power supply, I was considering doing this on its mains lead.
... which looks encouraging, but I also want to "filter" more on the incoming 12v. I also have the problem of "clicks" when using the encoder and you can hear "noise" when pressing the touch screen.
More info is that I will install a Nextion 5" screen at the weekend along with a second nano. I have some info on how to reduce the noise from the Nextion.
Evan, thanks for the info on calculating the required resistor size, that all makes sense as does the comment about the disc capacitor.
|
Peter
All this seems to point to a uBITX or BITX that is being run at near maximum? audio volume level.? I would probably look at RF and IF circuitry to see why it? is necessary to have the volume turned up so high.??
Receiver sensitivity should be in the 0.1 to 0.3 microvolt level for MDS (Minimum? Discernable Signal).? Have you set your BFO way outside the IF passband??? That might be something to look?at.? If the BFO is way outside the IF filter it? will appear that the receiver is insensitive and thus require turning the volume? (audio gain) to high levels.
If you have an audio amplifier that has a sensitive input you can use a 0.1 mfd? capacitor to couple that amplifier to the DC power lead.? It should show any? audio range noise.? If you use a diode detector ahead of this audio amplifier? you should be able to hear any RF noise that might be present on the DC? power leads.
You should be able to decrease AF noise on DC power lines by adding a 470 mfd to 2700 mfd capacitor between DC positive and DC negative (observe? polarity of the capacitors).??
RF on the power leads can usually be decreased by adding 0.1 mfd capacitors? across the DC supply lines, both at the power supply and at the power input to? the transceiver.
Arv
_._
It's definitely coming from the mains, if I switch off the soldering iron I get a <clack> on the audio of the radio, if I switch off the main light switch in the room I get an extremely loud <CLACK>. I have a PS30SWII switching power supply, I was considering doing this on its mains lead..
... which looks encouraging, but I also want to "filter" more on the incoming 12v. I also have the problem of "clicks" when using the encoder and you can hear "noise" when pressing the touch screen.
More info is that I will install a Nextion 5" screen at the weekend along with a second nano. I have some info on how to reduce the noise from the Nextion.
Evan, thanks for the info on calculating the required resistor size, that all makes sense as does the comment about the disc capacitor.
|
Keep all leads short or be prepared to add large and small caps at each end of the long leads because voltages can build up across stray inductance caused to long leads. Like a 10 MFD and a 0.1 disc ceramic (also with short leads) in parallel. A disc ceramic cap can be a problem at 20M and above if the leads are too long.
IBM axiom: "Anything can be done if it is logical. The only problem is implementation." An extension of this is a lot of small problems can jump out at the builder if too little thought is put into the process.
If something works satisfactorily, theory is no longer a factor.
Bob¡ª KK5R
On Thursday, July 9, 2020, 11:23:00 AM EDT, peter.mccracken@... <peter.mccracken@...> wrote:
Hi all, I want to build a dedicated power supply board mounted to the back of the case and remove the regulator that is currently on the raduino, I also want to try to "clean" as much noise as possible from the supply whilst doing this. I only have rudimentary knowledge of this stuff but the below is my attempt at designing something for this. The idea is to clean up the 12V supply before connecting it to the ubitx mainboard and also use a resistor to drop the voltage into the regulator somewhat before feeding that into the Raduino. I am not sure what value would be good for R2. I would be grateful for any suggestion as to how I could do this better.  Best regards, Peter.
|
I remember reading in an old spec sheet for a three-terminal regular that the operating voltage of the regulator was three volts. This no doubt depends largely on the design of the regulator but 3-4 volts should be considered operational. Keep in mind that if you use the maximum applied voltage, that means about 30 volts at the operating current needs to be dissipated unnecessarily because of the heat. Applying 12V is not excessive to me, though. Still, however, some kind of heat sink or fins on the three-terminal regulator is to me cheap insurance.
Bob ¡ª KK5R
On Thursday, July 9, 2020, 12:28:59 PM EDT, Evan Hand <elhandjr@...> wrote:
Peter,
Before you go through the trouble of building in the "noise" filter, I would first verify that the noise is coming from the 12 supply.? The best way to do that is to test the noise level on battery power.? You do not need to transmit, so any 12v battery capable of supplying 250 to 300 ma for a short time should do.? I have used a car jumper battery that I have and found little to no difference in the noise level on battery power vs mains supplied through either of my TexPower 13.8volt switching supplies. The noise is coming from the antenna in my neighborhood caused by QRM and high QRN noise levels on the air in general.
With the above understanding, I will make some suggestions for R2 to reduce the power dissipation of the 7805 regulator.? ?That does depend on the total current that you will need from the regulator, and THAT depends on what you have planned to add onto the rig that will need 5 volts.? If you add up the power requirements of all of the devices on the stock rigs, the total current is much less than 200ma, more like 120 ma (approximate, as I have not done all of the spec sheet validations? I did look up the stock version 6 2.8" display and that has a max of 80ma).? Then you have the minimum voltage that the 7805 needs to regulate to 5 volts.? I use 3 volts to get some safety margin.? That means you need to supply 5 + 3 = 8volts minimum at maximum current.? If the input voltage is truly 12 volts, and you want 8 volts to the regulator minimum at 200ma, and you need a 4volt drop at 200 ma, then 4/.2=20ohms.? That resistor will need to dissipate 4*0.2 = 0.8 watts.? All of these calculations are DC values, so the simple E=IR and P=EI and the transforms work.
For my rigs, I am adding second Nanos, larger displays with built-in GUI processors, and signal processors, so I have upped the max current to <1 amp (the maximum that the 7805 provided by HFSignals can regulate) and added other safety margins to get 4 ohms at 4 watts.? Were I to do it again, I would have added a second 7805 to supply the auxiliary equipment and not modified the Raduino board.
In general, the stock setup works well, and no changes are needed.? Adding a heatsink to the regulator can help if you are going to operate in high ambient temperatures.??
The other comment that I would make is that if you find you have RF noise from the power supply, then you will need to add capacitors to filter the higher frequency.? Something like a 0.1 to 0.01 uF ceramic disc.? The 470uF will not filter higher frequency stuff.? There is too high of internal resistance at RF in electrolytic capacitors.? You may also be better off to add an RF choke instead of the resistor.? I will let someone more knowledgable on that subject to make a true recommendation.
The above are my thoughts and should be verified before you take action on them.? I do make mistakes at times.
73
Evan
AC9TU
|
(Resending because when I reported that obvious SPAM about the 27 mil or whatever funds, I was auto-kicked from the group?! Weirdness. Very sorry if this is a repeat but guessing that my post was lost due to being booted. Weird.)
Mark ----- Forwarded Message -----
From: M W <rd232d@...> Sent: Saturday, July 11, 2020, 04:39:53 PM PDT Subject: Re: [BITX20] Building a 12V Supply Board
To get an efficient 12V to 5V regulator, you can look at the 7805 equivalent modules like the AMSRO1-7805 or the VXO7805, these are switching regulators so they are efficient but noisy so you might want to put them in a metal enclosure (a heat sink as part of the enclosure is a good idea) and put say a 10 uF and 0.1 uF capacitor right next to them, to reduce radiated noise. They are pretty much a drop-in replacement (double check that you have the pinout right though as otherwise you can let the magic silver-grey smoke out.)
You can search for such things on https://www.findchips.com/ - They cost me $2 or so each, not lots more than a regular 7805, and I tend to install those in anything battery-powered as you get ~90% efficiency, which beats the heck out of the ~42% efficiency you get out of a stock 7805 run on 12V! Reminds me to buy a few more. I'm putting some into a couple always-on AC powered devices just to reduce power costs on AC.
Mark
On Thursday, July 9, 2020, 06:36:15 PM PDT, Bob Lunsford via groups.io <nocrud222@...> wrote:
I remember reading in an old spec sheet for a three-terminal regular that the operating voltage of the regulator was three volts. This no doubt depends largely on the design of the regulator but 3-4 volts should be considered operational. Keep in mind that if you use the maximum applied voltage, that means about 30 volts at the operating current needs to be dissipated unnecessarily because of the heat. Applying 12V is not excessive to me, though. Still, however, some kind of heat sink or fins on the three-terminal regulator is to me cheap insurance.
Bob ¡ª KK5R
On Thursday, July 9, 2020, 12:28:59 PM EDT, Evan Hand <elhandjr@...> wrote:
Peter,
Before you go through the trouble of building in the "noise" filter, I would first verify that the noise is coming from the 12 supply.? The best way to do that is to test the noise level on battery power.? You do not need to transmit, so any 12v battery capable of supplying 250 to 300 ma for a short time should do.? I have used a car jumper battery that I have and found little to no difference in the noise level on battery power vs mains supplied through either of my TexPower 13.8volt switching supplies. The noise is coming from the antenna in my neighborhood caused by QRM and high QRN noise levels on the air in general.
With the above understanding, I will make some suggestions for R2 to reduce the power dissipation of the 7805 regulator.? ?That does depend on the total current that you will need from the regulator, and THAT depends on what you have planned to add onto the rig that will need 5 volts.? If you add up the power requirements of all of the devices on the stock rigs, the total current is much less than 200ma, more like 120 ma (approximate, as I have not done all of the spec sheet validations? I did look up the stock version 6 2.8" display and that has a max of 80ma).? Then you have the minimum voltage that the 7805 needs to regulate to 5 volts.? I use 3 volts to get some safety margin.? That means you need to supply 5 + 3 = 8volts minimum at maximum current.? If the input voltage is truly 12 volts, and you want 8 volts to the regulator minimum at 200ma, and you need a 4volt drop at 200 ma, then 4/.2=20ohms.? That resistor will need to dissipate 4*0.2 = 0.8 watts.? All of these calculations are DC values, so the simple E=IR and P=EI and the transforms work.
For my rigs, I am adding second Nanos, larger displays with built-in GUI processors, and signal processors, so I have upped the max current to <1 amp (the maximum that the 7805 provided by HFSignals can regulate) and added other safety margins to get 4 ohms at 4 watts.? Were I to do it again, I would have added a second 7805 to supply the auxiliary equipment and not modified the Raduino board.
In general, the stock setup works well, and no changes are needed.? Adding a heatsink to the regulator can help if you are going to operate in high ambient temperatures.??
The other comment that I would make is that if you find you have RF noise from the power supply, then you will need to add capacitors to filter the higher frequency.? Something like a 0.1 to 0.01 uF ceramic disc.? The 470uF will not filter higher frequency stuff.? There is too high of internal resistance at RF in electrolytic capacitors.? You may also be better off to add an RF choke instead of the resistor.? I will let someone more knowledgable on that subject to make a true recommendation.
The above are my thoughts and should be verified before you take action on them.? I do make mistakes at times.
73
Evan
AC9TU
|
To get an efficient 12V to 5V regulator, you can look at the 7805 equivalent modules like the AMSRO1-7805 or the VXO7805, these are switching regulators so they are efficient but noisy so you might want to put them in a metal enclosure (a heat sink as part of the enclosure is a good idea) and put say a 10 uF and 0.1 uF capacitor right next to them, to reduce radiated noise. They are pretty much a drop-in replacement (double check that you have the pinout right though as otherwise you can let the magic silver-grey smoke out.)
You can search for such things on https://www.findchips.com/ - They cost me $2 or so each, not lots more than a regular 7805, and I tend to install those in anything battery-powered as you get ~90% efficiency, which beats the heck out of the ~42% efficiency you get out of a stock 7805 run on 12V! Reminds me to buy a few more. I'm putting some into a couple always-on AC powered devices just to reduce power costs on AC.
Mark
On Thursday, July 9, 2020, 06:36:15 PM PDT, Bob Lunsford via groups.io <nocrud222@...> wrote:
I remember reading in an old spec sheet for a three-terminal regular that the operating voltage of the regulator was three volts. This no doubt depends largely on the design of the regulator but 3-4 volts should be considered operational. Keep in mind that if you use the maximum applied voltage, that means about 30 volts at the operating current needs to be dissipated unnecessarily because of the heat. Applying 12V is not excessive to me, though. Still, however, some kind of heat sink or fins on the three-terminal regulator is to me cheap insurance.
Bob ¡ª KK5R
On Thursday, July 9, 2020, 12:28:59 PM EDT, Evan Hand <elhandjr@...> wrote:
Peter,
Before you go through the trouble of building in the "noise" filter, I would first verify that the noise is coming from the 12 supply.? The best way to do that is to test the noise level on battery power.? You do not need to transmit, so any 12v battery capable of supplying 250 to 300 ma for a short time should do.? I have used a car jumper battery that I have and found little to no difference in the noise level on battery power vs mains supplied through either of my TexPower 13.8volt switching supplies. The noise is coming from the antenna in my neighborhood caused by QRM and high QRN noise levels on the air in general.
With the above understanding, I will make some suggestions for R2 to reduce the power dissipation of the 7805 regulator.? ?That does depend on the total current that you will need from the regulator, and THAT depends on what you have planned to add onto the rig that will need 5 volts.? If you add up the power requirements of all of the devices on the stock rigs, the total current is much less than 200ma, more like 120 ma (approximate, as I have not done all of the spec sheet validations? I did look up the stock version 6 2.8" display and that has a max of 80ma).? Then you have the minimum voltage that the 7805 needs to regulate to 5 volts.? I use 3 volts to get some safety margin.? That means you need to supply 5 + 3 = 8volts minimum at maximum current.? If the input voltage is truly 12 volts, and you want 8 volts to the regulator minimum at 200ma, and you need a 4volt drop at 200 ma, then 4/.2=20ohms.? That resistor will need to dissipate 4*0.2 = 0.8 watts.? All of these calculations are DC values, so the simple E=IR and P=EI and the transforms work.
For my rigs, I am adding second Nanos, larger displays with built-in GUI processors, and signal processors, so I have upped the max current to <1 amp (the maximum that the 7805 provided by HFSignals can regulate) and added other safety margins to get 4 ohms at 4 watts.? Were I to do it again, I would have added a second 7805 to supply the auxiliary equipment and not modified the Raduino board.
In general, the stock setup works well, and no changes are needed.? Adding a heatsink to the regulator can help if you are going to operate in high ambient temperatures.??
The other comment that I would make is that if you find you have RF noise from the power supply, then you will need to add capacitors to filter the higher frequency.? Something like a 0.1 to 0.01 uF ceramic disc.? The 470uF will not filter higher frequency stuff.? There is too high of internal resistance at RF in electrolytic capacitors.? You may also be better off to add an RF choke instead of the resistor.? I will let someone more knowledgable on that subject to make a true recommendation.
The above are my thoughts and should be verified before you take action on them.? I do make mistakes at times.
73
Evan
AC9TU
|
FYI I used an LM2596 dc to dc converter to drop the 13.8 vdc from P1 to 5vdc It¡¯s rated to 3a. I use it to feed my TDA 2030a audio amp, my SSM 2167 mic preamp/compressor and theRaduino ?board.I bent the raduino1 pin 4 up so it doesn¡¯t set into the socket thus isolating the 13.8 supply from the raduino board.seems to work well. I did put a choke on the 5vdc output wire and I don¡¯t have a problem with RF noise.-- ?
73
Mick VA3EPM?
|
Mark, do the new replacement 7805's also have a max input voltage of 35V or is it capable of higher voltage? Also, are they in the same package?
Bob ¡ª KK5R
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Mark ----- Forwarded Message -----
From: M W <rd232d@...> Sent: Saturday, July 11, 2020, 04:39:53 PM PDT Subject: Re: [BITX20] Building a 12V Supply Board
To get an efficient 12V to 5V regulator, you can look at the 7805 equivalent modules like the AMSRO1-7805 or the VXO7805, these are switching regulators so they are efficient but noisy so you might want to put them in a metal enclosure (a heat sink as part of the enclosure is a good idea) and put say a 10 uF and 0.1 uF capacitor right next to them, to reduce radiated noise. They are pretty much a drop-in replacement (double check that you have the pinout right though as otherwise you can let the magic silver-grey smoke out.)
You can search for such things on https://www.findchips.com/ - They cost me $2 or so each, not lots more than a regular 7805, and I tend to install those in anything battery-powered as you get ~90% efficiency, which beats the heck out of the ~42% efficiency you get out of a stock 7805 run on 12V! Reminds me to buy a few more. I'm putting some into a couple always-on AC powered devices just to reduce power costs on AC.
Mark
On Thursday, July 9, 2020, 06:36:15 PM PDT, Bob Lunsford via groups.io <nocrud222@...> wrote:
I remember reading in an old spec sheet for a three-terminal regular that the operating voltage of the regulator was three volts. This no doubt depends largely on the design of the regulator but 3-4 volts should be considered operational. Keep in mind that if you use the maximum applied voltage, that means about 30 volts at the operating current needs to be dissipated unnecessarily because of the heat. Applying 12V is not excessive to me, though. Still, however, some kind of heat sink or fins on the three-terminal regulator is to me cheap insurance.
Bob ¡ª KK5R
On Thursday, July 9, 2020, 12:28:59 PM EDT, Evan Hand <elhandjr@...> wrote:
Peter,
Before you go through the trouble of building in the "noise" filter, I would first verify that the noise is coming from the 12 supply.? The best way to do that is to test the noise level on battery power.? You do not need to transmit, so any 12v battery capable of supplying 250 to 300 ma for a short time should do.? I have used a car jumper battery that I have and found little to no difference in the noise level on battery power vs mains supplied through either of my TexPower 13.8volt switching supplies. The noise is coming from the antenna in my neighborhood caused by QRM and high QRN noise levels on the air in general.
With the above understanding, I will make some suggestions for R2 to reduce the power dissipation of the 7805 regulator.? ?That does depend on the total current that you will need from the regulator, and THAT depends on what you have planned to add onto the rig that will need 5 volts.? If you add up the power requirements of all of the devices on the stock rigs, the total current is much less than 200ma, more like 120 ma (approximate, as I have not done all of the spec sheet validations? I did look up the stock version 6 2.8" display and that has a max of 80ma).? Then you have the minimum voltage that the 7805 needs to regulate to 5 volts.? I use 3 volts to get some safety margin.? That means you need to supply 5 + 3 = 8volts minimum at maximum current.? If the input voltage is truly 12 volts, and you want 8 volts to the regulator minimum at 200ma, and you need a 4volt drop at 200 ma, then 4/.2=20ohms.? That resistor will need to dissipate 4*0.2 = 0.8 watts.? All of these calculations are DC values, so the simple E=IR and P=EI and the transforms work.
For my rigs, I am adding second Nanos, larger displays with built-in GUI processors, and signal processors, so I have upped the max current to <1 amp (the maximum that the 7805 provided by HFSignals can regulate) and added other safety margins to get 4 ohms at 4 watts.? Were I to do it again, I would have added a second 7805 to supply the auxiliary equipment and not modified the Raduino board.
In general, the stock setup works well, and no changes are needed.? Adding a heatsink to the regulator can help if you are going to operate in high ambient temperatures.??
The other comment that I would make is that if you find you have RF noise from the power supply, then you will need to add capacitors to filter the higher frequency.? Something like a 0.1 to 0.01 uF ceramic disc.? The 470uF will not filter higher frequency stuff.? There is too high of internal resistance at RF in electrolytic capacitors.? You may also be better off to add an RF choke instead of the resistor.? I will let someone more knowledgable on that subject to make a true recommendation.
The above are my thoughts and should be verified before you take action on them.? I do make mistakes at times.
73
Evan
AC9TU
|
The AMSRO1-7805 does 36V, the VXO7805 does 36V as well unless you set it up for -5V output (not what we want here.) These are a PC board with parts attached to make a switching module, they're not quite identical to a usual TO-220 plastic blob with metal tab but pretty close; Just insulate it from the heat sink, which isn't a bad idea with any regulator, to prevent shorting it out. Datasheets are always easy to get (though for new folks, understanding them may require some hairpulling, screams of dismay, etc., just ask on the list though and someone will help interpret.)
For an example of what they look like, see https://www.digikey.com/product-detail/en/dcomponents/AMSRO1-7805-NZ/2721-AMSRO1-7805-NZ-ND and https://www.digikey.com/product-detail/en/cui-inc/VXO7805-1000/102-4258-ND/ though that one doesn't appear to need a heat sink - Still I'd put 0.1 uF caps on input and output and (overdoing caps is a thing for me, cheap and prevents some problems) probably 10 uF caps both places as well. They changed things since my last order, it happens!
Mark
On Saturday, July 11, 2020, 06:11:41 PM PDT, Bob Lunsford via groups.io <nocrud222@...> wrote:
Mark, do the new replacement 7805's also have a max input voltage of 35V or is it capable of higher voltage? Also, are they in the same package?
Bob ¡ª KK5R
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Mark ----- Forwarded Message -----
From: M W <rd232d@...> Sent: Saturday, July 11, 2020, 04:39:53 PM PDT Subject: Re: [BITX20] Building a 12V Supply Board
To get an efficient 12V to 5V regulator, you can look at the 7805 equivalent modules like the AMSRO1-7805 or the VXO7805, these are switching regulators so they are efficient but noisy so you might want to put them in a metal enclosure (a heat sink as part of the enclosure is a good idea) and put say a 10 uF and 0.1 uF capacitor right next to them, to reduce radiated noise. They are pretty much a drop-in replacement (double check that you have the pinout right though as otherwise you can let the magic silver-grey smoke out.)
You can search for such things on https://www.findchips.com/ - They cost me $2 or so each, not lots more than a regular 7805, and I tend to install those in anything battery-powered as you get ~90% efficiency, which beats the heck out of the ~42% efficiency you get out of a stock 7805 run on 12V! Reminds me to buy a few more. I'm putting some into a couple always-on AC powered devices just to reduce power costs on AC.
Mark
On Thursday, July 9, 2020, 06:36:15 PM PDT, Bob Lunsford via groups.io <nocrud222@...> wrote:
I remember reading in an old spec sheet for a three-terminal regular that the operating voltage of the regulator was three volts. This no doubt depends largely on the design of the regulator but 3-4 volts should be considered operational. Keep in mind that if you use the maximum applied voltage, that means about 30 volts at the operating current needs to be dissipated unnecessarily because of the heat. Applying 12V is not excessive to me, though. Still, however, some kind of heat sink or fins on the three-terminal regulator is to me cheap insurance.
Bob ¡ª KK5R
On Thursday, July 9, 2020, 12:28:59 PM EDT, Evan Hand <elhandjr@...> wrote:
Peter,
Before you go through the trouble of building in the "noise" filter, I would first verify that the noise is coming from the 12 supply.? The best way to do that is to test the noise level on battery power.? You do not need to transmit, so any 12v battery capable of supplying 250 to 300 ma for a short time should do.? I have used a car jumper battery that I have and found little to no difference in the noise level on battery power vs mains supplied through either of my TexPower 13.8volt switching supplies. The noise is coming from the antenna in my neighborhood caused by QRM and high QRN noise levels on the air in general.
With the above understanding, I will make some suggestions for R2 to reduce the power dissipation of the 7805 regulator.? ?That does depend on the total current that you will need from the regulator, and THAT depends on what you have planned to add onto the rig that will need 5 volts.? If you add up the power requirements of all of the devices on the stock rigs, the total current is much less than 200ma, more like 120 ma (approximate, as I have not done all of the spec sheet validations? I did look up the stock version 6 2.8" display and that has a max of 80ma).? Then you have the minimum voltage that the 7805 needs to regulate to 5 volts.? I use 3 volts to get some safety margin.? That means you need to supply 5 + 3 = 8volts minimum at maximum current.? If the input voltage is truly 12 volts, and you want 8 volts to the regulator minimum at 200ma, and you need a 4volt drop at 200 ma, then 4/.2=20ohms.? That resistor will need to dissipate 4*0.2 = 0.8 watts.? All of these calculations are DC values, so the simple E=IR and P=EI and the transforms work.
For my rigs, I am adding second Nanos, larger displays with built-in GUI processors, and signal processors, so I have upped the max current to <1 amp (the maximum that the 7805 provided by HFSignals can regulate) and added other safety margins to get 4 ohms at 4 watts.? Were I to do it again, I would have added a second 7805 to supply the auxiliary equipment and not modified the Raduino board.
In general, the stock setup works well, and no changes are needed.? Adding a heatsink to the regulator can help if you are going to operate in high ambient temperatures.??
The other comment that I would make is that if you find you have RF noise from the power supply, then you will need to add capacitors to filter the higher frequency.? Something like a 0.1 to 0.01 uF ceramic disc.? The 470uF will not filter higher frequency stuff.? There is too high of internal resistance at RF in electrolytic capacitors.? You may also be better off to add an RF choke instead of the resistor.? I will let someone more knowledgable on that subject to make a true recommendation.
The above are my thoughts and should be verified before you take action on them.? I do make mistakes at times.
73
Evan
AC9TU
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You can use a 7808 or 7809 between the 12/13.8V and the 7805 to split the dissipation
The AMSRO1-7805 does 36V, the VXO7805 does 36V as well unless you set it up for -5V output (not what we want here.) These are a PC board with parts attached to make a switching module, they're not quite identical to a usual TO-220 plastic blob with metal tab but pretty close; Just insulate it from the heat sink, which isn't a bad idea with any regulator, to prevent shorting it out. Datasheets are always easy to get (though for new folks, understanding them may require some hairpulling, screams of dismay, etc., just ask on the list though and someone will help interpret.)
For an example of what they look like, see and though that one doesn't appear to need a heat sink - Still I'd put 0.1 uF caps on input and output and (overdoing caps is a thing for me, cheap and prevents some problems) probably 10 uF caps both places as well. They changed things since my last order, it happens!
Mark
On Saturday, July 11, 2020, 06:11:41 PM PDT, Bob Lunsford via <nocrud222= [email protected]> wrote:
Mark, do the new replacement 7805's also have a max input voltage of 35V or is it capable of higher voltage? Also, are they in the same package?
Bob ¡ª KK5R
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Mark ----- Forwarded Message ----- Sent: Saturday, July 11, 2020, 04:39:53 PM PDT Subject: Re: [BITX20] Building a 12V Supply Board
To get an efficient 12V to 5V regulator, you can look at the 7805 equivalent modules like the AMSRO1-7805 or the VXO7805, these are switching regulators so they are efficient but noisy so you might want to put them in a metal enclosure (a heat sink as part of the enclosure is a good idea) and put say a 10 uF and 0.1 uF capacitor right next to them, to reduce radiated noise. They are pretty much a drop-in replacement (double check that you have the pinout right though as otherwise you can let the magic silver-grey smoke out.)
You can search for such things on - They cost me $2 or so each, not lots more than a regular 7805, and I tend to install those in anything battery-powered as you get ~90% efficiency, which beats the heck out of the ~42% efficiency you get out of a stock 7805 run on 12V! Reminds me to buy a few more. I'm putting some into a couple always-on AC powered devices just to reduce power costs on AC.
Mark
On Thursday, July 9, 2020, 06:36:15 PM PDT, Bob Lunsford via <nocrud222= [email protected]> wrote:
I remember reading in an old spec sheet for a three-terminal regular that the operating voltage of the regulator was three volts. This no doubt depends largely on the design of the regulator but 3-4 volts should be considered operational. Keep in mind that if you use the maximum applied voltage, that means about 30 volts at the operating current needs to be dissipated unnecessarily because of the heat. Applying 12V is not excessive to me, though. Still, however, some kind of heat sink or fins on the three-terminal regulator is to me cheap insurance.
Bob ¡ª KK5R
On Thursday, July 9, 2020, 12:28:59 PM EDT, Evan Hand < elhandjr@...> wrote:
Peter,
Before you go through the trouble of building in the "noise" filter, I would first verify that the noise is coming from the 12 supply.? The best way to do that is to test the noise level on battery power.? You do not need to transmit, so any 12v battery capable of supplying 250 to 300 ma for a short time should do.? I have used a car jumper battery that I have and found little to no difference in the noise level on battery power vs mains supplied through either of my TexPower 13.8volt switching supplies. The noise is coming from the antenna in my neighborhood caused by QRM and high QRN noise levels on the air in general.
With the above understanding, I will make some suggestions for R2 to reduce the power dissipation of the 7805 regulator.? ?That does depend on the total current that you will need from the regulator, and THAT depends on what you have planned to add onto the rig that will need 5 volts.? If you add up the power requirements of all of the devices on the stock rigs, the total current is much less than 200ma, more like 120 ma (approximate, as I have not done all of the spec sheet validations? I did look up the stock version 6 2.8" display and that has a max of 80ma).? Then you have the minimum voltage that the 7805 needs to regulate to 5 volts.? I use 3 volts to get some safety margin.? That means you need to supply 5 + 3 = 8volts minimum at maximum current.? If the input voltage is truly 12 volts, and you want 8 volts to the regulator minimum at 200ma, and you need a 4volt drop at 200 ma, then 4/.2=20ohms.? That resistor will need to dissipate 4*0.2 = 0.8 watts.? All of these calculations are DC values, so the simple E=IR and P=EI and the transforms work.
For my rigs, I am adding second Nanos, larger displays with built-in GUI processors, and signal processors, so I have upped the max current to <1 amp (the maximum that the 7805 provided by HFSignals can regulate) and added other safety margins to get 4 ohms at 4 watts.? Were I to do it again, I would have added a second 7805 to supply the auxiliary equipment and not modified the Raduino board.
In general, the stock setup works well, and no changes are needed.? Adding a heatsink to the regulator can help if you are going to operate in high ambient temperatures.??
The other comment that I would make is that if you find you have RF noise from the power supply, then you will need to add capacitors to filter the higher frequency.? Something like a 0.1 to 0.01 uF ceramic disc.? The 470uF will not filter higher frequency stuff.? There is too high of internal resistance at RF in electrolytic capacitors.? You may also be better off to add an RF choke instead of the resistor.? I will let someone more knowledgable on that subject to make a true recommendation.
The above are my thoughts and should be verified before you take action on them.? I do make mistakes at times.
73
Evan
AC9TU
|
The best way to prevent noise is to use a linear regulator as you only have to flatten out the 60 hz line noise and prevent rf from the radio getting back into it.
As far as the raduino goes, it uses the 7805, a linear regulator and is by nature quiet.? If you are concerned about heat add a heat sink.? You might consider a couple diodes in series rather than a resistor.?
Other regulators in the radio include the arduino, as well there is another 7805 to control the bias of the drive MOSFETs.
all the best
Dave
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Bob Lunsford
Mick
_Dave_ AD0B