Since I have such a terrible habit of blowing stuff up and not really knowing 100% of everything I request help in double checking that I wired my simplistic power supply circuit properly. Thanks! (Schematic attached)

 

27 views and not one criticism so I'll call it a win.

 

The function of this device is not clear.

 

D1,D2 are pointless,they are being shorted out by Sw2, also you have both -5V, and -12V shorted to ground, otherwise you need to explain what you're trying to achieve.

 

D1,D2 are pointless,they are being shorted out by Sw2, also you have both -5V, and -12V shorted to ground, otherwise you need to explain what you're trying to achieve.

D1 and D2 maintain the outputs while SW2 is in between contacts during switching. This is the product of another thread on here.
I agree about the -5V and -12V being shorted.
Also I am not sure that the supply will switch on if Pw is connected to ground through R1 and LED1 rather than directly to ground. TS will need to verify that this does actually work with the particular supply proposed for this design.

 

I can see a potential problem with the DMP1 instrument, between supply and measurement inputs.

When measuring on the 12V supply, the measurement inputs will be 3V above the supply.

Then either the instrument must have a galvanic separation on the supply, otherwise a DC / DC converter with galvanic separation instead of VR1 should be used.

 

More resistance for your LEDs? That's over 40ma on the 3v? Are you trying to light a room?

 

D1 and D2 maintain the outputs while SW2 is in between contacts during switching. This is the product of another thread on here.
I agree about the -5V and -12V being shorted.
Also I am not sure that the supply will switch on if Pw is connected to ground through R1 and LED1 rather than directly to ground. TS will need to verify that this does actually work with the particular supply proposed for this design.

Pw led1 and resistor in line with the ground pull-up resistor of the supply has been tested to work successfully. You are definitley correct about the issues with shorting the -12 and -5v lines to ground, I should probabally just leave them disconnected. I apologize that I cannot include a wire diagram of the PSU as it is so old that there is nothing on the internet about it. (Silencer Atx 275)

 

You are definitley correct about the issues with shorting the -12 and -5v lines to ground, I should probabally just leave them disconnected.

Yes, if you are not using them then don't connect them to anything.

 

I can see a potential problem with the DMP1 instrument, between supply and measurement inputs.

When measuring on the 12V supply, the measurement inputs will be 3V above the supply.

Then either the instrument must have a galvanic separation on the supply, otherwise a DC / DC converter with galvanic separation instead of VR1 should be used.

The cheap Chinese schematic for VR1 simply state that the power must be half of what you are measuring (with a minimum of 9v. I do believe the instrument has a independent ground so it should be fine. The schematic for vr1 is attached should you be interested.

 

More resistance for your LEDs? That's over 40ma on the 3v? Are you trying to light a room?

The LED Calculator I am using says that for a source voltage of 3.3v and a voltage drop of 2.0-2.2v at 20ma the required resistor is 68 ohms. Is something incorrect with my methods?

 

Your image for VR1 shows it to be using an ICL7107. The following is from the '7107 datasheet and indicates that you do have a problem here.

That is, the input voltages must be within the range of the supply voltage

 

The LED Calculator I am using says that for a source voltage of 3.3v and a voltage drop of 2.0-2.2v at 20ma the required resistor is 68 ohms. Is something incorrect with my methods?

No, I miscalculated, although I would use 10ma, for most LED indicators 20ma is max current. They will be super bright. Often even 5ma works.

 

No, I miscalculated, although I would use 10ma, for most LED indicators 20ma is max current. They will be super bright. Often even 5ma works.

Very true. I'm going to recalculate my resistor values for 10ma for the resistors I have. I get by using 75ohms, 270ohms and 560 ohms in various parallel and series combonations.

 

Your image for VR1 shows it to be using an ICL7107. The following is from the '7107 datasheet and indicates that you do have a problem here.
View attachment 125297
That is, the input voltages must be within the range of the supply voltage

It is not a 7107 sorry for the misinformation, it's using a NTE 1910. Not sure if the problem is still there if I'm using a 1910.

 

The NTE1910 is a voltage regulator not a voltmeter??

 

Confusion reigns!

In your post #10 you include a schematic for the voltmeter referring to it as VR1 (but your original post uses VR1 to refer to the voltage regulator).
That post #10 schematic shows the voltmeter using the ICL7107 chip. If the voltmeter you have does use that chip then the problem remains.

 

Confusion reigns!

In your post #10 you include a schematic for the voltmeter referring to it as VR1 (but your original post uses VR1 to refer to the voltage regulator).
That post #10 schematic shows the voltmeter using the ICL7107 chip. If the voltmeter you have does use that chip then the problem remains.

Confusion indeed! I now see what you mean to an extent regarding 7107. In the Chinese manual it states something along the lines of "supply voltage must be half of the measuring range" or something of the sorts. I was moderately confused by this and assumed that since it's a 9v rated meter and I'm only reading up to 12v that I should be fine. However this must not be so! May you please elaborate on how I might go about solving this issue?

 

1. You could use a 9V battery to power the meter.
2. Derive an isolated 9V some other way, e.g. an isolated DC-DC converter.
3.Use a balanced to unbalanced converter, perhaps like the one below.

The first two allow the power supply to float while the third 'moves' the 12V referenced input to a ground reference.

 

1. You could use a 9V battery to power the meter.
2. Derive an isolated 9V some other way, e.g. an isolated DC-DC converter.
3.Use a balanced to unbalanced converter, perhaps like the one below.

The first two allow the power supply to float while the third 'moves' the 12V referenced input to a ground reference.
View attachment 125453

So from what I understand now, due to the fact that it's an isolated ground meter, I cannot have the supply and the input on the same common ground. I'm now trying to think of options because I don't want 2 separate mains plugs for this thing and a 9v battery will be a last resort. Too bad I don't have a schematic for my psu power supply. I wonder if I could possibly wire a seperate inverter into the mains cable and run it off that? I'm not sure how far this common ground thing goes.. or even if it was possible to run it off mains at all......