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Isolator circuitry
Posted: Tue Jun 10, 2014 8:25 pm
by PatchWar
Hi, I'm currently using the pi to program a microcontroller and I want to keep both the pi and microcontroller isolated from the rest of my circuit. I was hoping to use some opto-isolators however I am having trouble finding any that will work. I need one that will work off of 9mA with a Bandwidth of at least 3 MHz. Don't have to be opto-isolators... Anyone know a solution?
Re: Isolator circuitry
Posted: Tue Jun 10, 2014 8:35 pm
by hampi
If I understand the problem correctly: you need to power both the RPi and microcontroller from a battery during the system tests. A small lead acid battery with 5 V converter is suitable for this.
Re: Isolator circuitry
Posted: Wed Jun 11, 2014 2:57 pm
by Sproing
I'm sure others will have a much better idea, but maybe something like a 6N137?
http://pdf.datasheetcatalog.com/datashe ... NW2611.pdf
Re: Isolator circuitry
Posted: Fri Jun 13, 2014 1:54 pm
by PatchWar
Thanks, I was looking at the 6N137 and they seem to be a good fit as you said. Slight inconvenience that they are inverting however, I'm sure I could just swap the anode/cathode and have one side go to 3.3V through a current limiting resistor. In case anyone else was wondering, there are some very high bandwidth isolators from Texas Instruments that I found as well.
ISO7140FCC being one of them
The disadvantage of a high bandwidth capability is that it introduces more noise in your channel as well, something to keep in mind for those needing high bandwidth capabilities.
Thought I'd post my findings and hope it may be useful to some others out there.