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Power supply question
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Your powersupply will only supply the amount of current the radio needs.
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So for your powersupply , you will have no problem and it will only be loaded with a few amps , depending if your in rx or tx mode. Joe VE1BWV On Fri, Jun 1, 2018, 1:47 PM <n2tmc@...> wrote: I have a 13.8 volt 20 amp supply I use on my 2 meter rigs. It has multiple connections for power out. Will my BITX40 only use the amps it needs or am I going to blow it up? I am sorry if this is a dumb question but since my stroke my memory isn't always that great. |
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Should work fine.
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I'd add a 3 Amp fuse inline on the +12v from power supply? to Bitx40 to keep explosions down to a minimum. Jerry On Fri, Jun 1, 2018 at 09:47 am, <n2tmc@...> wrote: I have a 13.8 volt 20 amp supply I use on my 2 meter rigs. It has multiple connections for power out. Will my BITX40 only use the amps it needs or am I going to blow it up? I am sorry if this is a dumb question but since my stroke my memory isn't always that great. |
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Hi George,
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If you don't know (remember) and you ask a question then it isn't a dumb question :) Your power supply does not 'force' 20 amps. It tries to 'force' 13.8 volts and it will until it gets to somewhere around 20 Amps *if* the load (your radio) demands. So the short answer is that your radio will only take the current it needs as long as it is not more than that 20 Amps the power supply can deliver. Your 20 Amp supply will be loafing along powering your happy ubitx. On 06/01/2018 12:47 PM, n2tmc@... wrote:
I have a 13.8 volt 20 amp supply I use on my 2 meter rigs. It has --
bark less - wag more |
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Bill, that is a great answer!
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Al On Jun 1, 2018, at 12:56 PM, Bill Cromwell <wrcromwell@...> wrote: |
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Assuming there is nothing wrong with the rigs the excess current the supply can put out will not be used and you are safe.?? It is just like in your house, the AC outlet can put out lots of current,but each device will only take what is needed as long as the voltage is in the required range. I often run my ubitx off a 50 amp Astron supply. de ku4pt On Fri, Jun 1, 2018 at 12:47 PM, <n2tmc@...> wrote: I have a 13.8 volt 20 amp supply I use on my 2 meter rigs. It has multiple connections for power out. Will my BITX40 only use the amps it needs or am I going to blow it up? I am sorry if this is a dumb question but since my stroke my memory isn't always that great. |
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I believe 13.8 is considered the upper limit for the uBITX main board.? It should work fine as-is, but I wouldn't push it any hotter.
If you wanted to be extra careful, you may want to put a 12v voltage regulator like a LM7812 inline with the main board's power.? The PA power line (brown wire, IIRC) can run off the higher voltage just fine and may get you a bit more power even. |
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You may use a higher voltage.? A regulator and appropriate capacitors might seem like a wise choice, but a regulator such as an LM340-12 requires a minimum 2.5-volt difference between the input and output voltage, so a regulator won't do the job unless you have a 14.5V DC input.? And that's the minimum. The Texas Instruments datasheet shows an LM340-12 operating with a 19V input and a 12V output.
The TDA2822 amplifier chip has an upper voltage input of +15V.? The bipolar (2N3904 and 2N3906) transistors can handle a voltage as high as 30V.? The FETs (IRF510) can handle up to 30V.? Likewise, the 78L05 voltage regulator that biases the FETs can handle an input voltage as high as 30V.? The relays on my board (HFD27/012S) have a recommended coil voltage of 12V, but the voltage can go as high as 24V without harm.? There are several diodes across relay coils, but without a bill of materials I can't determine a reverse-voltage rating for them but it's likely above 13.8 volts. Have fun. -- Jon Titus, KZ1G Herriman, UT USA |
¿ªÔÆÌåÓýThe LM1085-12 has a dropout voltage of 1.3v typ; 1.5v max.?? The lm1117ADJ likewise has a low dropout voltage but would require a couple more parts since that part doesn¡¯t come in a fixed 12v version. Mike K5ESS ? From: [email protected] [mailto:[email protected]] On Behalf Of Bo Barry ? If I recall correctly the 3 terminal regulators definitely need a minimum of 3 volts difference between input and output. |
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A couple of 5amp or 10amp Silicon diodes (5 watt rating) will give you a
voltage drop of about 1.2v or 12.6v feeding the board. I had to crank up my power supply to 15.1v to get a consistent 12v out of a 7812 feeding the mainboard. tim ab0wr On Sat, 02 Jun 2018 08:25:45 -0700 "KE0GYC" <dragonfanatic90@...> wrote: I believe 13.8 is considered the upper limit for the uBITX main |
I agree with your voltages for the discrete devices. |
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