Re: Perfect tiny backpack setup?
#qmx
Leigh,
What's your plan for a logging program? Is it part of digipi? Is it something separate that runs on the phone/tablet (not easy integration if we're just VNC to the pi)?
--
73 Jim K1IR
|
Back in the early 1980's while I worked my way through university as a bench-tech doing more than a thousand VHF/UHF radios over those years I was given a set of ceramic trimmer tools. It eliminated that entire sequence of adjust, remove tool, measure, add tool, adjust, remove tool... I could adjust while measuring without influencing the RF characteristics of the circuit. It even worked fine for doing those tiny multi-turn pots with the brass screw and the trimcaps and the hex tool for doing the slugs in inductors when peaking the helical coils.
If you do an amazon search on "8pcs adjust frequency anti static ceramic screwdriver kit" you will find what I currently use.
The original tools were just a piece of ceramic that was jammed in to a wad of rubber that was inserted in to a tiny cardboard tube.
Be careful, ceramic is very fragile and you can't do anything more than trimming adjustments, never use it as a conventional screwdriver. But it beats the pants off of those plastic tools or the ones with the tiny metal tips.
--
Tisha Hayes, AA4HA
Sr Engineer, 4RF Inc.
|
Re: QDX - protection of BS17O PA
Thank you Sverre,?? I went to the link you provided and saw and read what I think I need to do.? Hope I can work you when I get my QDX's finished and tested.???
Take care and have fun.
73 Dave WA5DJJ
|
Re: QDX - protection of BS17O PA
Dear Sverre,
Thank you for your explanation and you website that did a really good job of telling me what I wanted to know.? I will go find me some 47V Zenner diodes.?
Take care and have fun. I hope to work you on my QDX's when I get them finished and tested.
73 Dave WA5DJJ
SUPER QRSS/WSPR GRABBER
|
Re: QDX - protection of BS17O PA
Gary,
I totally agree with your comments using a TVS. That’s the right way to do it. Zener is a poorman’s junk box solution. Zeners can be found in junkbox, at least in my case and TVS are more specialty diodes :)
I use zener diodes in all my design radios and now on my QDX and QMX, no PA BBQ problems so far after my initial QDX PA hiccups.
73
Barb WB2CBA
|
Re: Short circuit in buck converter QMX
Has any of the boards ever failed with the unable to shutdown symptom after a few minutes of normal operation? Initial investigation D101 seem to have failed short.
My kit also had q103/q104 short. This was after I did the current limited power up and the current went up to 180ma. I then discovered rev H of the assembly manual describing the issue. I then removed the short and the rest went as described. I then proceeded to check cw rx and tx function all good. I then proceeded to check digi modes and plugged in the USB. Wspr was received normally. I shut it down or maybe power cycled because I needed to move it to another usb port and the symptom appeared. USB does not detect a device and the qmx powers up shows welcome screen, 20m and after a few seconds "shutdown!".
|
Re: #QMX #BPF problems with fault finding
#qmx
#bpf
Chris,
I think I will go for BPF bypass straight away. In this way I will confirm that this is were problem lies.
I located T401 input connection but I need to confirm <RX_IN> side. Do you mean C401-C402-C404 common point? I think there was typo in your previous post so I need be sure.
Can I shorten these two points or do I need to unsolder and disconnect T401 input side and connect to <RX_IN> using short jumper wire.
Thx.
---------------------------------
73 de Marek SP9TKW
|
Don, The audio amplifier for the headphone jack is IC404. You should check it for proper bias voltages. I didn't see if you wired the radio for 9v or 12v, but you should find a little less than half that voltage on pins 1,2,3,5,6&7 of IC404. That voltage is supplied by a resistive voltage divider made up of R423 and R424. If those voltages are good, then you will need to inject an audio signal into the inputs (it's a stereo amp connection) pins 2 and 6 and look for them to come out on the left and right channels. If that test is good, then you may have an issue with the D/A converter IC401or the RC filter circuit between it and IC 404. Refer to the schematic and parts layout diagram for the above parts. Good luck ... Ron
On Sun, Sep 3, 2023 at 5:33?AM K9NUD-Steve < k9nud@...> wrote: I overheated my headphone jack on the initial assembly. I swapped it with the PTT jack to get up and running. It's not uncommon, these little jacks can't handle much heat.
|
Re: QDX - protection of BS17O PA
Transient Voltage Suppression (TVS) devices are more appropriate protectors than Zeners. They are designed to absorb overvoltage transients and react faster than Zeners which are designed to operate as voltage regulators. Zeners also have much larger shunt capacitance.
Transient Voltage Suppressors (TVS) and Zener diodes are both used to absorb excess energy and protect your circuit from damage when voltage levels spike above the device’s clamping voltage. What’s the difference between them?
Comparing the two, TVS diodes have a faster response time (ns level) and a higher surge current absorbing ability, making them more suited to instant circuit protection against transient voltage spikes. When a TVS diode suffers from high transient voltage, the diode’s resistance changes from high to low very quickly, absorbing the transient current and protecting your delicate downstream devices. Then the voltage is clamped down to a fixed value to prevent high peak voltage from damaging your protected chips.
Gary
W9TD
|
Re: #qmx Don’t Use USB-C PD to power your QMX?!
#qmx
Hi Evan?
Yes that could be a possibility too. Doing it on the supply rail isn't because there's a capacitor on the potential divider which slows everything down too much. Yes perhaps a fast loop could run just for 5V protection.
Another possibility nobody has mentioned, if hardware modifications are to be contemplated, is just making the zener diodes bigger. What about changing the 500mW zener to a 5W type?
It also all depends what "problem" we are trying to "solve". Being able to cope with a sudden jump in supply voltage from 6V to 12V? Or something more?
On Sun, Sep 3, 2023, 3:03 PM Evan Hand < elhandjr@...> wrote: Hans,
Is it possible to set an interrupt routine based on time to sample the 5-volt input and shut down the output when it reaches a threshold value greater than 5 volts but less than the 5.6-volt zener voltage?? If the timing of the power loop is 1 ms, the fast interrupt loop would need to be on the order of 0.25 ms to be effective.? This would be a very short routine to sample and shut down only.? I have used this concept in industrial control systems to handle alarm conditions with insufficient processor capability to run the entire program within the required time.?
An alternative is to store the value of the input voltage and turn off the PWM signal until the voltage stabilizes for several slower control loop cycles.
There are many strategies possible with the fast timed interrupt loop.??The A-to-D conversion times do come into play.? For the control situation, a direct read capability bypassed normal I/O processing.
73
Evan
AC9TU
|
Re: #qmx Don’t Use USB-C PD to power your QMX?!
#qmx
Hi all
I agree a series resistor would prevent the GPIO conflict. The GPIO pin is necessarily configured as push-pull. A series resistor would reduce the efficiency of the buck converter. However my feeling is that if the resistor was small, say 220 ohms, it would suffice to resolve the fight and not significantly impact the efficiency.?
Gunnar, I'd like to understand why you're so sure the current through the zener and base-emitter is low? I agree as soon as the voltage rises it will stop the PWM and thus further energy being delivered into the inductor. My point is by this time significant additional energy was already delivered into the inductor which at 330uH, isn't tiny. Before the voltage rise could be detected and switch off the PWM. The energy will be dissipated through the zener and base-emitter. So my question is how are we so sure that it is "quite low", not a current spike which can kill the base-emitter junction? I'm just nervous because in my experience dumping even small energy into transistors via the base, was a quick death...
On Sun, Sep 3, 2023, 3:03 PM Evan Hand < elhandjr@...> wrote: Hans,
Is it possible to set an interrupt routine based on time to sample the 5-volt input and shut down the output when it reaches a threshold value greater than 5 volts but less than the 5.6-volt zener voltage?? If the timing of the power loop is 1 ms, the fast interrupt loop would need to be on the order of 0.25 ms to be effective.? This would be a very short routine to sample and shut down only.? I have used this concept in industrial control systems to handle alarm conditions with insufficient processor capability to run the entire program within the required time.?
An alternative is to store the value of the input voltage and turn off the PWM signal until the voltage stabilizes for several slower control loop cycles.
There are many strategies possible with the fast timed interrupt loop.??The A-to-D conversion times do come into play.? For the control situation, a direct read capability bypassed normal I/O processing.
73
Evan
AC9TU
|
Hi all,
I have had a QDX for a few years. I built it and made it for 9 volts. It has done a great job with over 500 grids worked. In the past I might have made 20 contacts in a day but recently that number has diminished. This week I might have 1 contact. The power out put on 40, 30 and 20 is around 3.8 watts into a very good EFHW antenna. I always use a tuner to reduce pressure on the finals. Also, my clock is synced correctly. I use WSJT, Logview and Gridtracker.
So, here is my question and I don't know anything about this. Can there be a problem with the signal that is being sent? I have ruled out all mechanical issue that I can but a station will answer my CQ and then they never complete the exchange. I answer a station and get a reply and then nothing else. Very frustrating and it is getting worse as time goes on.
Any suggestions?
73, Dean
N2TNN
|
I overheated my headphone jack on the initial assembly. I swapped it with the PTT jack to get up and running. It's not uncommon, these little jacks can't handle much heat.
|
Re: #qmx Don’t Use USB-C PD to power your QMX?!
#qmx
Hans,
Is it possible to set an interrupt routine based on time to sample the 5-volt input and shut down the output when it reaches a threshold value greater than 5 volts but less than the 5.6-volt zener voltage?? If the timing of the power loop is 1 ms, the fast interrupt loop would need to be on the order of 0.25 ms to be effective.? This would be a very short routine to sample and shut down only.? I have used this concept in industrial control systems to handle alarm conditions with insufficient processor capability to run the entire program within the required time.?
An alternative is to store the value of the input voltage and turn off the PWM signal until the voltage stabilizes for several slower control loop cycles.
There are many strategies possible with the fast timed interrupt loop.??The A-to-D conversion times do come into play.? For the control situation, a direct read capability bypassed normal I/O processing.
73
Evan
AC9TU
|
Re: #qmx Don’t Use USB-C PD to power your QMX?!
#qmx
Hello Hans,
first of all, I am not the inventor of this solution, but I think it is a good one.
I'll try to answer your questions :
1) No, I have not tried it and I am reluctant to put my QMX to the test. I would humbly suggest that you do it, if you agree to my arguments below
2) if you read the text it is proposed to put a resistor in series with the GPIO coming from the processor. It is not in the diagram though.
3) I do not agree with your analysis.
As soon as the zener starts to conduct, the PWM signal is clamped to ground. So no more energy is fed to the 330uH inductor.
The current through the zener will be quite low, so wether the zener nor the transistor will suffer.
There will be no current spike.
As soon as Vcc goes below the zener+base/emitter voltage the clamp on the PWM will be removed and the processor will continue to adapt to the new input voltage, not even knowing the the over-voltage protection was engaged
br SM5EIE/Gunnar
|
Re: #qmx Don’t Use USB-C PD to power your QMX?!
#qmx
My first impression was "What a neat hack!" ?but there are a few unanswered issues besides the ones Hans brings up:
Did you change D108 to a 5V zener? ?Which one? What's the reverse leakage current on that zener? What's the pulldown resistance? What's the transistor? What's the turnon voltage that'll shut down the SMPS pin? More generally, given all the above, what's the Vcc voltage that'll disable the PWM_5V signal? What's the CPU pin configured as, and what are the results of shorting it to ground? [Only Hans knows...] If you put a resistance into the PWM_5V line to reduce the current, how does that effect the drive signal?
73, Willie N1JBJ
toggle quoted message
Show quoted text
On Sep 3, 2023, at 7:05 AM, Hans Summers <hans.summers@...> wrote:
Hi Gunnar, all
A few comments/questions...
1) this circuit has been proposed, but has anyone actually tried it for real, and then verified that on the step change from 6V to 12V it does protect the circuit without killing the zener?
2) As far as I can see the transistor will be shorting the processor's GPIO pin directly to ground. In other words the transistor will be fighting whatever transistor is inside the microcontroller. Does this worry anyone??
3) More fundamentally... Does it work at all, even theoretically? So the voltage input suddently jumps from 6V to 12V. The SMPS is then running at a too high duty cycle and the voltage at the SMPS therefore jumps. Ordinarily the 5.6V zener is supposed to eat this spike by passing the current to ground. It has to do that for up to 2ms until the processor control loop detects the situation and acts to fix it. Apparently that couple of milliseconds is a bit too much for a 0.5W zeners and there is a possibility of killing it. Which brings me to my question. Now that same current is going through the zener and though the base-emitter junction of the transistor. It could be for a much shorter time because it will (hopefully) win the fight with the GPIO pin and shut down the PWM; still, by that time substantial energy has been stored in the 330uH inductor and now that has to dissipate as a current pulse onto the base-emitter junction of the transistor. Why is the transistor going to survive this?
|
Re: #qmx Don’t Use USB-C PD to power your QMX?!
#qmx
Hans, The proposed circuit has problems but the concept shows promise.? I didn't look at it very carefully. I saw the issue of "?the transistor will be shorting the processor's GPIO pin directly to ground. In other words the transistor will be fighting whatever transistor is inside the microcontroller." That could be fixed by adding a resistor in series with the GPIO output pin to limit the GPIO pin's current when the transistor turns on.? I haven't looked at the other more difficult questions you bring up or whether this fixes the input voltage jump issue at all or is it not a robust fix.? I do though like the idea of a "dead-man switch" so no matter what the software is doing, the circuit should have some hardware protection if it can be implemented at very low hardware cost with relatively few components.? OMG the density, the density of that wonderful 3D art packaging.? One can't appreciate it until you get the plugging all the boards together in the final assembly steps!
-Steve K1RF
------ Original Message ------
Date 9/3/2023 7:05:52 AM
Subject Re: [QRPLabs] #qmx Don’t Use USB-C PD to power your QMX?!
Hi Gunnar, all
A few comments/questions...
1) this circuit has been proposed, but has anyone actually tried it for real, and then verified that on the step change from 6V to 12V it does protect the circuit without killing the zener?
2) As far as I can see the transistor will be shorting the processor's GPIO pin directly to ground. In other words the transistor will be fighting whatever transistor is inside the microcontroller. Does this worry anyone??
3) More fundamentally... Does it work at all, even theoretically? So the voltage input suddently jumps from 6V to 12V. The SMPS is then running at a too high duty cycle and the voltage at the SMPS therefore jumps. Ordinarily the 5.6V zener is supposed to eat this spike by passing the current to ground. It has to do that for up to 2ms until the processor control loop detects the situation and acts to fix it. Apparently that couple of milliseconds is a bit too much for a 0.5W zeners and there is a possibility of killing it. Which brings me to my question. Now that same current is going through the zener and though the base-emitter junction of the transistor. It could be for a much shorter time because it will (hopefully) win the fight with the GPIO pin and shut down the PWM; still, by that time substantial energy has been stored in the 330uH inductor and now that has to dissipate as a current pulse onto the base-emitter junction of the transistor. Why is the transistor going to survive this?
|
These can also be found for around the same price on eBay sold by rapidonline. Free postage too.?
|
Re: #qmx Don’t Use USB-C PD to power your QMX?!
#qmx
Hi Gunnar, all
A few comments/questions...
1) this circuit has been proposed, but has anyone actually tried it for real, and then verified that on the step change from 6V to 12V it does protect the circuit without killing the zener?
2) As far as I can see the transistor will be shorting the processor's GPIO pin directly to ground. In other words the transistor will be fighting whatever transistor is inside the microcontroller. Does this worry anyone??
3) More fundamentally... Does it work at all, even theoretically? So the voltage input suddently jumps from 6V to 12V. The SMPS is then running at a too high duty cycle and the voltage at the SMPS therefore jumps. Ordinarily the 5.6V zener is supposed to eat this spike by passing the current to ground. It has to do that for up to 2ms until the processor control loop detects the situation and acts to fix it. Apparently that couple of milliseconds is a bit too much for a 0.5W zeners and there is a possibility of killing it. Which brings me to my question. Now that same current is going through the zener and though the base-emitter junction of the transistor. It could be for a much shorter time because it will (hopefully) win the fight with the GPIO pin and shut down the PWM; still, by that time substantial energy has been stored in the 330uH inductor and now that has to dissipate as a current pulse onto the base-emitter junction of the transistor. Why is the transistor going to survive this?
|
Re: QMX Shipped, panic stage
#qmx
Billy, et al,
If you are going to continue building kits like this you definitely need this:
| |
Tisha Hayes, AA4HA
Barb WB2CBA
Marek SP9TKW
Ronald Taylor
Gary W9TD
K9NUD-Steve
David Wilcox K8WPE