I have a precision burden box, whose burdens are switched by a rotary switch, and there are 21 positions. I want to make it "digital controllable", that is, using MCU to switch between these burdens. The current flow through the burden may be 10A max. Now I list the possible methods I know. In all method, I need to consider the current capacity and on resistance, and
for some methods, I need take more into consideration.
- Using solid state relays. (The on resistance and current capacity maybe a problem.)
- Using MOSFETs. (I need work more on the driving circuit and heat-sink design, as well as the space maybe a problem.)
- Using electro-mechanical relays. (The on resistance maybe a problem. Is there a relay with Ron comparable with a rotary switch, that is, <10 mOhms? )
- Using a stepper motor to drive the rotary switch. (If using open-loop, I can't know exactly the position of the 'wiper', so it may not be reliable.)
That's what I know for now. Can someone give me some suggestions on the possible methods, or some recommendations on parts selection.
Best Answer
Is this being used for AC, DC, or both?
What is the highest voltage that will be across an open switch contact?
Do all switch positions need to handle your full current rating?
How fast does the switch position need to change?
My gut tells me to use relays for this. They are inexpensive and have contact resistance comparable to a rotary switch. But I also like your idea of using some form of motor drive (servo, whatever) to drive the existing rotary switch. Position feedback can be arranged.
Bottom line: we can give you a better answer if you provide more information.