Adding digital voltage meter to cicuit

[ragingben]

Hi guys, I'm new here and brand new to electronics in general. I'm trying to build a battery starve cirucit for taking a 9v dc input (from a PSU) and it uses a 10k pot to allow you to simulate a dying battery. I found the circuit online here.

The whole project is availabe here.

Instead of an analog meter I want to use a mini digital one, that requires 5v dc.

In my haste I ran ahead and purchased one of these which is probably a heap of junk, but was pretty small.

How would I go about wiring this is into the circuit? I know I have to step down the 9v to 5v, can I do this with a 2.2k resistor? If I add this to the circuit will it mean that the pot will get the remaining 4v? I'm pretty stuck, but I know this is pretty easy. I'm a software guy trying to get into hardware, and so far I'm boggled

 

[duke37]

The voltage drop with a resistor will vary with the current taken by the meter which is not good. The best way would be to use a 5V voltage stabiliser, these are very common as many computer circuits run on 5V.
1A voltage stabitiser 7805, this is protected against short circuit and over temperature but not being connected the wrong way round. A capacitor may be needed at the output (0.1 to 10 microF) to stabilise the system if you have long wires.

 

[ragingben]

Hi duke37, thanks for taking the time to answer.

So I need to get a 5V stabalizer (is this the same as a regulator?) Is this the kind of thing?

Do I run a wire on from the 9v in jack in parrallel to the one that goes to VR1, to the stabalizer? Or do I run a wire from the same point where the current would be fed to the 10K pot? It is vital I can get 9v at the 10K pot.

Like I said I'm really, really new to electronics (I didn't even do it when I was in school"), I'm ordering a few books to read up on it so hopefully I won't be so clueless for long.

 

[duke37]

I should have said regulator!
I attach a diagram of how it should be connected.
You say that it is vital that you have a 9V supply. You may have one of these but many small unregulated supplies vary quite a lot, they are high with a low load. I would not be surprised at 12V unloaded. Check with you posh voltmeter.

Duke

 

[ragingben]

thank you very much duke,i realy appreciate it.im away until sunday but i will check it out on monday!thanks again

 

[ragingben]

thank you very much duke,i really appreciate it!i am away until sunday night,but i will check it out monday,thanks again