Programmable current supply

[jonasforssell]

Dear Forum,

I have been searching high and low for a simple low cost programmable current supply.
Here are the specs I am looking for:

Square wave with duty cycle 0-100% and 0-30 Hz
0-1 A programmable current level
minimum 5V minimum voltage level

There are plenty of waveform generators around but they do not support a programmable current level
There are also programmable power supplies but they often have a 1 second resolution which is too slow
I can find Source Measure Units but they are very very expensive

I was hoping to find something for around 100 USD. Preferrable with a graphical interface.
I am not really interested in building anything myself unless there is a ready made arduino shield or similar with software.

Many thanks for your feedback.
/Jonas

[VinzC]

I assume you might need to build your own if you find nothing suitable. However more details are necessary to provide an elaborated answer.

• You specified the minimum output voltage but unfortunately that doesn't make much sense for a current source. Instead you should specify either the load resistor range (if you happen to know it) or the *maximum* output voltage
• What rise and fall times are you expecting? If you don't know or it doesn't matter will just give more design freedom.
• How do you want that current source "programmed" ? Via a potentiometer? Via serial communication such as SPI, I²C...? Via voltage?
• You also mentioned a square wave with duty cycle 0-100% and 0-30 Hz; does that mean you want that device to have its own controls? If so under what form? (see above question)

[jonasforssell]

Thank you for your reply.

The voltage does not require to be higher than 5V. Normal operation voltage will be around 3V
Rise and fall times are not specific but less than 10 ms would be preferred.
I would prefer the unit to be an independent one with a screen and its on user interface (like an oscilloscope or a function generator) but I can also consider programming from a PC.

The closest I have got is the Uni-T UDP3305S but I cannot determine if is capable of the frequencies I am looking for and it is also a bit on the high cost side.

[VinzC]

Indeed any power supply unit that happens to be programmable is likely to address your requirements. On the other hand, they are fairly simple and easy to implement¹... except the control / graphical interface, which is non trivial. Other than that you might even build your own implementation with an Arduino, if a quick-n-dirty™ DIY circuit fits your needs. In that case, you can even use a laptop to provide the user interface.

See "voltage-controlled current sources", for instance. You'll come across many examples that use an operational amplifier and a MOSFET. Low-side and high-side variations are all possible.

[Terry Bites]

For bipolar operation and precise results use this circuit.
$10ish in parts. Io=Vin/Rset, simple. Many inst amps will work, not most of the single supply types though.
It's fast enough for your purposes.
A picture even. Draw people. Burnt sticks on the wall even, buy a phone with a camera!

.