# Signal voltage converter 5 to 20v

Discussion in 'General Electronics Chat' started by airmiles, Nov 13, 2010.

1. ### airmiles Thread Starter New Member

Nov 9, 2010
1
0
I need to make a voltage converter for 0-5v input to 10 -20v output, Vout = (2 x Vin) +10. The input is from an air fuel controller in a car and the output voltage will be read by a panel meter:

3½ 12v Digital Red LED 20V DC Volt panel meter

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=370365501275

I found this voltage doubler circuit posted on here that does most of what I need,

Will the above circuit need exactly 12v to work accurately, would it be ok on about 14.5v with the engine running?

I also need a steady 5v supply for the panel meter, could I get that from the above circuit?

Also I need to add the 10v somehow, I may be able to add a digit on the panel meter itself by shorting the led's, the meter will never actually show 20v, it's always going to be somewhere between 10v and 19v.

Where is the best place to source the components, I've found many of them on ebay but individually, is there somewhere I could easily get everything needed from, Maplins?

Thanks
Tom

2. ### mik3 Senior Member

Feb 4, 2008
4,846
69
Use an op amp with a gain of 2 to amplify the signal by 2 and then use a summing amplifier to add the 10V offset.

3. ### Jaguarjoe Active Member

Apr 7, 2010
770
91
There are two problems here. First, using the car's raw electrical for power is suicidal. There are more spikes and dips and possible huge voltage swings than immagineable. Second, you can not get 20 volts from an op-amp powered with less than 20 volts.

Divide the MAF signal by 10 to get 0- .5 volts. Multiply by 2 to get 0- 1 volt. Add 1 volt to get 1- 2 volts. Make a well protected +5 volt supply powered from your 14.5, or steal some +5 from the car's sensor power. Use the ICL7660 part to make -5 volts. The only hang up here is that you'll need a 0- 2 volt meter. Maybe you can dissect your 20 volt unit and see if it can change ranges thru jumper settings. Or, bite the bullet and spend 6 more pounds for a new meter.

4. ### mik3 Senior Member

Feb 4, 2008
4,846
69
It is possible to use a boost converter to get 24V.

5. ### Jaguarjoe Active Member

Apr 7, 2010
770
91
You'll need an op-amp that can run from +24v. The TL062/72/82 all have a max supply of 18 volts.