BOB 9118 Opto Isolator

Have a good idea for a new product for SFE or Olimex? Let us know!

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D_Heidner
Posts: 9
Joined: Tue Oct 21, 2014 2:00 pm

BOB 9118 Opto Isolator

Post by D_Heidner » Wed Dec 14, 2016 3:35 am

Would you please consider making a revision / update to the 9118 OptoIsolator breakout board?

Currently the design assumes that the local controlling device will be driving the LED's And that the open collector transistor outputs will be used to drive the remote circuit.

However another use for the board is to provide isolation such that you don't have ground loops when working with analog data acquisition projects. In this case the remote device may still be a low voltage Arduino/PI/etc... but the open collector from the breakout boards are driving inputs on the local board. Think of desiring to monitor simple snap switch inputs and providing isolation to the project.

However because the BOB9118 has the grounds connected on the LED side of the optical isolators the only solution is to left the pad and run a jumper over to the unused pin on the header. It would be more useful to run each LED cathode to its on pin on the board and simply allow the user to decide to connect the cathodes together.

Another possibility would be to allow a simple cut on the circuit board to be made... unfortunately that run that connects the two together is done UNDER the opto-isolator. The only choice is to cut and lift one of the cathode connections on the chip... not a very clean solution.

darrellg
Posts: 321
Joined: Fri Oct 17, 2014 10:02 am
Location: Southern California

Re: BOB 9118 Opto Isolator

Post by darrellg » Wed Dec 14, 2016 10:14 am

Opto-isolators are pretty simple devices and are readily available in DIP packages far cheaper than this BOB. Have you considered ordering one from Digikey or Mouser and doing it on your own?

D_Heidner
Posts: 9
Joined: Tue Oct 21, 2014 2:00 pm

Re: BOB 9118 Opto Isolator

Post by D_Heidner » Wed Dec 14, 2016 5:48 pm

I have a stash of opto isolators already.

But I was also trying to create little projects that others could follow and build. Suggesting that they cut a pin and solder a jumper to it removes the value of suggesting people use the BoB9118. Separating the cathodes seems like a good choice if they revise or update the board. Make the channels independent.

Note - no reference to any site... just suggested for SFE when revising or introducing optical isolation breakout boards.

darrellg
Posts: 321
Joined: Fri Oct 17, 2014 10:02 am
Location: Southern California

Re: BOB 9118 Opto Isolator

Post by darrellg » Thu Dec 15, 2016 12:13 pm

Your suggestion definitely makes sense, especially since there in a no-connection pin right there.

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