A question about ODC5R


A question about ODC5R
The customer used ODC5R to control the DC24V relay. It has failed for two ODC5R in two consecutive months. Each ODC5R module has been in normal use for about a month.
Malfunction: the channel indicator light on ODC5R is not bright, but the relay it controls is in a closed state. When I pull out the terminal block on ODC5R, the relay loses power.
The control of the relay is very simple, but the operation is very frequent.
1, is there any problem in using this way?
2, if there is no problem, what is the cause of the failure?
I’ve changed to ODC5I, and I’ll watch it for a while.


The http://documents.opto22.com/1949_SNAP_Reed_Relay_Modules_Data_Sheet.pdf says the relay contacts can handle 416 mA at 24 volts. It also says to use a commutating diode when switching inductive loads. Since the load is a relay, does it have the required transient protection diode, and does it pull more than 416 mA when actuated?


The module has a very small reed relay, in your application the contacts are welding together, so the output is always on. The module LED switches correctly, but the contacts are always closed due to its failure.
As @dougm said, you must use a diode at the least, but in short, you have the wrong module for the application.


This is indeed our fault.
Customers use this kind of relay. The working current is only 40mA and the action current is 60mA. Because the current is very small, he does not use commutating diodes.
Excuse me
1, now the customer has used IDC5-i instead of ODC5R. Is it necessary to use commutating diodes?
2. Is the commutating diode model 1N4005?

Thank you very much.


Without a flyback diode, you could be hitting hundreds of volts across the reed relay when it opens from the inductive flow of the relay coil. Adding a 1N4005 should work fine for a flyback diode, I’ve used them on 24VDC coils without issue. Install them at the relay coil terminals is best.

Another option is to get a relay that has a diode accessory. It will be less likely for it to fall out in the future, and no way for someone to put the diode in the wrong way. More expensive, but cheaper than a new module.


By the way, Omron MY2N-D2-GS would have the diode built-in. Looks like they are buying the kind without the diode. Probably very little cost difference.


Very strange. I tested the customer’s problematic ODC5R in the office. Let it move at a very high frequency, 10 times faster than the scene, and run normally for 24 hours.


Electrical noise and wire length can be quite different in the field causing the voltage spikes to be considerable higher. Just like others indicated you would want the diodes. I have experienced these issues in my past also with other manufacturers of REED’s and the diode helped.


Are you sure a ODC5R is the best module to be using for this? Since you know you are controlling a 24VDC coil, I think you could use a ODC5A or ODC5SNK/SRC. You still should have a diode on your coil, but these modules would probably be more forgiving (they have a diode across their outputs already). You will also get a longer warranty on those modules.


Thank you for your help.
The use of ODC5R is just because there are such modules in the customer’s spare parts.
It has been corrected according to your suggestion.

  1. Replace ODC5R with ODC5-i.
    2, replace MY2N-GS with MY2N-D2-GS with flyback diode.
    Thanks again!


Excuse me
If we use snap ODC-32 module to control DC24V relay, is it necessary to rectified diode?
Thank you!