Pages: [1]   Go Down
Author Topic: replacing pushbutton in unknown circuit with optoisolator  (Read 416 times)
0 Members and 1 Guest are viewing this topic.
Offline Offline
Newbie
*
Karma: 1
Posts: 28
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

I have successfully replaced a push button with an optoisolator for arduino control of an unknown circuit. Everything works fine so far but I wish to know if I might run in to trouble later. I measured the current across the switch of the unknown circuit as 1.6mA. I'm using a Sharp pc817 optoisolator which has a CTR of 50% and a max current of 50mA. on one side of the optocoupler (LED Side) is an arduino output pin and a 150 Ohm resistor to limit current. On the other side (transistor side) I put no resistor at all. is this OK? I assumed that the current will be limited to 1.6mA so there was no need for one but I'm not sure if it is safe.
Logged

United Kingdom
Offline Offline
Tesla Member
***
Karma: 220
Posts: 6587
Hofstadter's Law: It always takes longer than you expect, even when you take into account Hofstadter's Law.
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

What you have done sounds OK, provided that the voltage across the pushbutton or optoisolator output when the button is not pressed is low enough. Have you measured that voltage?
Logged

Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

Offline Offline
Newbie
*
Karma: 1
Posts: 28
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Hi dc.
I have, it's ~12V. The pc817 has the following max ratings on the output:

Collector-emitter voltage, VCEO: 35 V
Emitter-collector voltage, VECO: 6V
Logged

Pages: [1]   Go Up
Jump to: