0
\$\begingroup\$

I have designed a circuit with some resources from this website and I attached it here. I have given circuit connection in a breadboard and successfully run and control the speed of the motor. After a while, I moved on to the pad-per-hole PC prototyping PC board. I have given the same connection on that board. But there is no output from pad-per-hole PC prototyping PC board.

I checked connection thrice but there seem no flaws in connection. I have measured voltage in a circuit. It is as follows.

Input voltage for optocoupler - 1.2 V in breadbaord and 1.17V in pad-per-hole PC board. Output voltage(between c and E in phototransistor) - 0.005 V (in pad-per-hole board) Could not find what is the problem in pad-per-hole PC prototyping PC board connection. What might be the problem? enter image description here

\$\endgroup\$
  • \$\begingroup\$ What is a "dot board"? Is it a pad-per-hole PC prototyping PC board? If so, it may not have the holes connected in the same way (or at all) as the plastic breadboard. \$\endgroup\$ – Peter Bennett Oct 12 '17 at 19:53
  • \$\begingroup\$ Yes. It is a pad-per hole PC prototyping PC board. Sorry, I actually didn't know the correct technical name for that board. I have checked for continuity with a multimeter. There is no continuity problem. Actually, in that pad-per-hole PC board, an input voltage to the optocoupler is 0.3 or 0.4V lesser than the input needed for the optocoupler. (i.e) 1.17V or 1.18V instead of 1.2V input. \$\endgroup\$ – Dhans Oct 13 '17 at 4:06
1
\$\begingroup\$

enter image description here

Figure 1. Test points for circuit debugging.

The circuit is so simple that debugging should not present a problem.

  • You have checked the voltage on the opto-LED. Double-check that the polarity is still right. Pin 1 should be positive with respect to pin 2.
  • With the LED off you should have 24 V at (1), 0 V at (2) and 24 V at (3).
  • With the LED on D1 should clamp the voltage rise at (2) to 5 V or so. The voltage at (1) should be a few hundred millivolts above that at (2). The voltage at (3) should be close to zero.

It's really just a matter of logically going through the circuit. When an unexpected voltage is found then you need to figure out the reason.

\$\endgroup\$
  • \$\begingroup\$ Ok, will check and let you know! \$\endgroup\$ – Dhans Oct 13 '17 at 8:04
  • \$\begingroup\$ I have tested all above points. Here are the details of value. At (1) potential difference is 24V as you said, At (2) value is 0V and 22.9V at (3). I felt two incidents that occurred while checking with my board. Accidentally I have shorted emitter and collector of the phototransistor and motor starts to run even if the Optocoupler LED is off. After that, I have measured voltage pin 1 of the optocoupler and it shows 20.3V. I was shocked. What is the problem here? Am I burnt optocoupler? Note: I connected SMPS 24V supply's ground and arduino gnd pin as common ground. \$\endgroup\$ – Dhans Oct 13 '17 at 10:49
  • \$\begingroup\$ You forgot to mention whether those measurements were taken with the opto LED on or off. With the opto-isolator there is no need to connect the two circuit grounds but it shouldn't cause any problems. If you really have 22.9 V on pin 1 of the opto then your micro will be damaged. \$\endgroup\$ – Transistor Oct 13 '17 at 11:13
  • \$\begingroup\$ Currently, I could not get any output from my uno \$\endgroup\$ – Dhans Oct 13 '17 at 13:09

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.