# Current to voltage transformer **URL:** \ **Category:** PCB Design\ **Created:** [November 28, 2011, 2:52pm UTC](https://community.sparkfun.com/t/current-to-voltage-transformer/22635 "2011-11-28T14:52:15Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![RobertD](https://avatars.discourse-cdn.com/v4/letter/r/b19c9b/32.png) [@RobertD](https://community.sparkfun.com/u/RobertD)\ **Post date:** [November 28, 2011, 2:52pm UTC](https://community.sparkfun.com/t/current-to-voltage-transformer/22635/1 "2011-11-28T14:52:15Z")
Hi folks, I need to input voltage to the analog input of arduino referenced to 3.3v, problem is the source is current. I look at op-amps and find they need +5 and -5 , the arduino board only supplies +5 and ground. How can I do this? Is there another way to wire the sensor to get 1- 2.5v, from a variable resistor sensor? ---
**Author:** ![Valen](https://avatars.discourse-cdn.com/v4/letter/v/9dc877/32.png) [@Valen](https://community.sparkfun.com/u/Valen)\ **Post date:** [November 29, 2011, 8:56am UTC](https://community.sparkfun.com/t/current-to-voltage-transformer/22635/2 "2011-11-29T08:56:20Z")
How much current are we talking about? In general, a simple resistor creates a voltage drop when current flows through it.One side of it connected to ground, that’s as simple as it can be. Or perhaps a resistor divider might be in order. But it might be better also if you tell more about that ‘variable resistor sensor’ or whatever circuit you have. ---
**Author:** ![RobertD](https://avatars.discourse-cdn.com/v4/letter/r/b19c9b/32.png) [@RobertD](https://community.sparkfun.com/u/RobertD)\ **Post date:** [November 29, 2011, 1:25pm UTC](https://community.sparkfun.com/t/current-to-voltage-transformer/22635/3 "2011-11-29T13:25:59Z")
Thanks Valen, I’m using a 5V pressure sensor, single pole to ground with variable resistance from 250 ohms to 40 ohms. I could divide the voltage with resistors to 3.3v but if I use 5v I can plug it directly in the Arduino A/D input. I was using a passive current to voltage circuit as per figure 2: [http://en.wikipedia.org/wiki/Current-to … \_converter](http://en.wikipedia.org/wiki/Current-to-voltage_converter). Worked fine but caused problems with communication for some reason, when I disconnected the sensor, I had no problem with connecting to the arduino. I even think I fried something inside, maybe too much current in the A/D pin. I’m considering an opamp but supply is a problem. Maybe a converter chip can give me -5v from +5v/G…? ---
**Author:** ![RobertD](https://avatars.discourse-cdn.com/v4/letter/r/b19c9b/32.png) [@RobertD](https://community.sparkfun.com/u/RobertD)\ **Post date:** [November 29, 2011, 1:29pm UTC](https://community.sparkfun.com/t/current-to-voltage-transformer/22635/4 "2011-11-29T13:29:52Z")
I would prefer to use the passive converter since precision doesn’t have to be perfect, just consistent. ---
**Author:** ![rrpilot](https://avatars.discourse-cdn.com/v4/letter/r/6de8d8/32.png) [@rrpilot](https://community.sparkfun.com/u/rrpilot)\ **Post date:** [November 29, 2011, 1:40pm UTC](https://community.sparkfun.com/t/current-to-voltage-transformer/22635/5 "2011-11-29T13:40:54Z")
Which sensor are you using? ---
**Author:** ![RobertD](https://avatars.discourse-cdn.com/v4/letter/r/b19c9b/32.png) [@RobertD](https://community.sparkfun.com/u/RobertD)\ **Post date:** [November 29, 2011, 4:19pm UTC](https://community.sparkfun.com/t/current-to-voltage-transformer/22635/6 "2011-11-29T16:19:32Z")
An oil pressure sensor. ---
**Author:** ![rrpilot](https://avatars.discourse-cdn.com/v4/letter/r/6de8d8/32.png) [@rrpilot](https://community.sparkfun.com/u/rrpilot)\ **Post date:** [November 30, 2011, 1:12pm UTC](https://community.sparkfun.com/t/current-to-voltage-transformer/22635/7 "2011-11-30T13:12:42Z")
You don’t want to be any more specific than that? A datasheet would be nice. ---
**Author:** ![RobertD](https://avatars.discourse-cdn.com/v4/letter/r/b19c9b/32.png) [@RobertD](https://community.sparkfun.com/u/RobertD)\ **Post date:** [November 30, 2011, 2:23pm UTC](https://community.sparkfun.com/t/current-to-voltage-transformer/22635/8 "2011-11-30T14:23:52Z")
Thanks, as Valen said, a voltage divider will suffice, with a reference voltage, should do the trick… 🙂 Sometimes I tend to go overboard with complications. ---
**Author:** ![rrpilot](https://avatars.discourse-cdn.com/v4/letter/r/6de8d8/32.png) [@rrpilot](https://community.sparkfun.com/u/rrpilot)\ **Post date:** [November 30, 2011, 2:57pm UTC](https://community.sparkfun.com/t/current-to-voltage-transformer/22635/9 "2011-11-30T14:57:36Z")
Okay that’s fair. I like to explore those options too, its fun to at least evaluate them in your head. Honestly I didn’t really understand what your sensor was doing at first which is why I asked for the datasheet but after reading it now it makes sense what you’re trying to do. 🙂