| Electronics > Projects, Designs, and Technical Stuff |
| DIY Voltmeter/Ammeter for lab power supply |
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| Microcheap:
Recently I've decided to revive an old project that was abandoned for some time. It is a simple voltmeter and ammeter display to be used in a bench power supply I was putting together. I was not worried with high precision my main concern was to make some thing easy to assembly with what I already have on hands so I tried to use only jellybean parts. Schematics and source files are linked bellow. I'm using this project more as an exercise to learn how to use Kicad and this is also the first board that I make using SMD components. I have used a bit of assembly and the CCS PIC-C to program PICs before, but I took the opportunity to learn the xc8 compiler too. So please, forgive me for any mistakes I have made and any critique/suggestion of improvements will be more than welcome. cheers |
| Kleinstein:
The capacitors C10 and C14 are perfectly fine and do not cause oscillation. Usually they should be same size, so more like 1 nF both. There is no need for D5/D6 - the OP has the same supply as the µC, so no higher voltage expected here. Before the voltage regulator it might take another 100 nF capacitor to ground. C15 at the fan control is a little odd. For just on/off use it would be more like a problem. For linear control, it would need another resistor at the transistor (at the emitter or base) to get more voltage swing to work with and the transistor likely needs to be a little higher power for linear control. It is a little odd to use an HC595 shift register for the 5 lines to the LCD - the more normal way would be having enough pins at the µC. There may be enough pins, when using those for ISP. The CAL switch might use a different way. |
| Simon:
You can of course buy relatively cheap panel meters but if it is an excersize then fair enough. |
| wasyoungonce:
--- Quote from: Simon on November 30, 2018, 02:38:36 pm ---You can of course buy relatively cheap panel meters but if it is an excersize then fair enough. --- End quote --- Yeah but aren’t those cheap panel meters very low refresh rate? Would be good for 3 times or more per second. Depends how the calculations are performed. Averaging will quicken them up Sent from my iPhone using Tapatalk |
| Simon:
why how fast can your brain process a reading and care about it? I think several times a second on a 20 quid meter is usual. |
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