morpheous87

Hi, I want to make this VA meter project for my 0-30V power supply unit(also project from here). I have a few questions about the VA meter. http://electronics-lab.com/projects/test/007/index.html is the project. - The power suplly, can exceed the 30V limit, and to be aroun 31-32V for example. The maximum input voltage for the VA meter is 30V, can this be harmfull for the VA meter? - One of the VA meter's inputs gets positive power directlly after the bridge rectifier. On the schematic the limits are 14-35V. In order the power suplly transformer has 2x30V windings, after the rectifier I expect voltage value above the 35V maximum? - Can I use separate 5V power supply only for the VA meters( with common ground with the power supply) This is for the current moment :)+ Best Regards!

I want to ask, if the power supply gives 3A at 30V, can it give ~7A at 12V when charging 12V batteries ?

How much A should it be?

I did some work on the case for the PSU, but after I finish one of the PCBs doesn't work anymore. Perhaps a piece of wire could sortened something. But I clear the PCB several times, but the fuse continue to break. Somethimes the fuse is OK and I measured some values, but I'm not sure where exactly to measure. For sure the input voltage from the transformer is OK, after the filter capacitors also is good. What to measure ? May be the OAMPs? I want to find the problem before I replace all of the parts on the PCB :) P.S. I think the input fuse is with low value. I put a bigger one and now it's working fine. How much should be the fuse for two PSUs and the transformer - 250VA 2x30V ?

That's the problem, I thnk to use it in series and parallel also.

I have two working PCBs for the PSU. Now I'm trying to make LCDs which will display the voltage and the current. I'm going to use Arduino for measurment and voltage deviders. My question is, could I use only one Arduino board to measure voltage and current from both PCBs (because of the common ground, which I should use for the Arduino board)?

The main filter capacitor is formed by 2 4700uF. Yestarday without the zeners on the OAMPs, the ouput voltage went over 31V. Now when both PCBs are powered the input voltage from the transformer is 33,5V.

On the first of the PCBs I put 2 4,7V zeners, on the second i put 4,7V on U2 and 5,1V on U1 (i hadn't one more 4,7V). When only one of them is turned on (the one with the 2 4,7V) has 30,4V ouput. When I turn and the second one on, maximum output is 29,7V. The PCB with the 5,1V zener has ~ 27V when both are turned on. So I suggest to put less than 4,7V zeners (4,3V may be) ?

Could be used 5,1V or 5,6V zeners instead of 4,7V ?

How much Watts should be the 4V7 zener?

PicMaster's version has 3 OAMPs, so I need 3 zener diodes on their positive pins?

I've made 2 PicMaster's version PCBs. They are working well. Since now I had a transformer only for one PCB, so I ordered a new transformer, which can supply both power supplies. The ordered transformer should be with 2 secondaries without common on 31 without load (so approximately 29-30V with load). Now I got it, but the company did a mistake as I see. The transformer have 33,5V without load, I think they did it on 31V with load. I tried one PCB with it. The input voltage is between 32-33,5V ( tried it with a DC motor on 13V 1,5A). There weren't any problems, but should I make some changes on the schematic to use this transformer. May be if I turn on both PCBs the input voltage will drop more, but still it will be over 30V I think. What to do?

I have a question about Arduino and PSU connections. In way I use pin2 on TB4 for common ground, how could I measure the voltage drop across TB4 ( it's on the groung signal path). I measured the voltage drop with common + and the two sides on the TB4, but I measured it with a multimer, with Arduino I need common ground. So I think the shunt resistor should be on the + ouput?

redwire This is the pdf I used to build my PSU. I'm not sure that the R7 you're talking about is the R7 in the pdf. Could you check is there some differences. Note that part's names on the last pdf's page (mounting diagram) is different from the part list page. Thanks for the help! EL_power_supply.pdf

I want to made a V-A multimer for the 30V PSU based on Aduino platform. So I have some questions about it. I need a voltage devider so the maximum voltage be <5 and put it in analog Arduino's pin. But how this devider should look? And for the current measurment I need a resistor to measure the voltage from both sides. Can the 82R resistor be used for this purpose (in PicMaster's version it's 2W resistor)?