Hi,
We're looking for someone that can design a bipolar current generator, voltage controlled.
We need the tested schematic (and routing suggestions if needed) but we can design the PCB.
It must meet the following specifications:
- powered by +-12v (if you want to go single-supply we can discuss it)
- +-50mA max output current
- 0.5% or better precision
- controlled by a 0-2.5v or a 0-4.096v source. A few digital pins are available if you need them.
- stable over three twisted pairs 1.5m long cables in parallel
The following control methods are both acceptable:
- one single voltage source, with output Iout=(Vin-offset)*K. Example: 0-2.5v input. 0V in, -50mA out. 2.5V in, +50mA out. 1.25V in, 0mA out.
- one single voltage source plus a polarity digital input. Iout=Vin*K*(-PinBinaryStatus). Example: 0V in, digital in low/high, 0mA out. 2.5V in, digital in low, -50mA out. 2.5V in, digital in high, +50mA out.
Secondary design goals:
- to be easily configured to a +-3A version for low resistance loads swapping a few components.
- Provide an Altium schematic
Two design suggestion:
It’s a bipolar current generator, voltage controlled.
The circuit was drafted by a physics professor with 30 years of experience in analog design, but due to personal reasons he was been unable to complete the job.
Of course it’s not complete. It’s necessary to pick the transistors (probably darlington or maybe FETs), the opamp and to do the stability analysis and compensate the feedback network.
The wire connecting the load connected to ground (tagged with “S”) is about 1 meter long, so it needs to be well stabilized.
It needs to operate in DC mostly, so better stable than fast.
The circuit is thought to operate in a broad range, from mA to A depending on Rref.
The circuit is supposed to power
Translations of the sentences in Italian:
* misura di i (measure of the current)
* campione hall (hall sample. you can consider it like a resistor with 2m of wire)
* generatore di corrente… (bipolar current generator with the load connected to ground on one side)
Hand drawn schematic attached.
Use costant current dummy load to limit the current of a costant-voltage source, with a similar design as Dave's dummy load. https://www.eevblog.com/2010/08/01/eevblog-102-diy-constant-current-dummy-load-for-power-supply-and-battery-testing/
Connect the load to a H-bridge made with FET (jfet or mosfets) isolated with optocouplers, which can be used to invert the current polarity.
The current used by the FETs is negligible. A circuit like this could be easily adapted to a broad range of source and output voltages and currents.
This offer is from Fermium LABS srl, my company.
https://fermiumlabs.com https://frm.li/datifattYou need to be able to produce a regular invoice, especially if you are in the EU.
To apply write an email to d@fermiumlabs.com with subject "costant current generator" or something like that.
Davide Bortolami,
Fermium LABS srl