Diode supression of relay back emf
Diode supression of relay back emf
(OP)
I am using a 12V relay to operate a DC motor in a motorcoach. I was wondering how important it is in this application to use back emf supression diodes across the relay coil. Do I really need to care about the energy spikes being put back on the 12VDC supply line? I had already put them in my circuit as a "sure, why not" but then realized that I now need to add a full-wave bridge to protect against reverse input polarity. I would like to drop the relays and the bridge if they are not really needed.





RE: Diode supression of relay back emf
TTFN
RE: Diode supression of relay back emf
It IS good practice to supress, and a small, cheap "no polarity" way to do it is a "ZNR" disc . Digi-key sells a n 18vdc rated part for .27 (p7282-nd)
RE: Diode supression of relay back emf
Thanks artym for your suggestion. I have seen surge absorbers used in other applications, but didn't think to use one here. There is a cost increase over a diode, but I'll save on not using the full-wave bridge.
RE: Diode supression of relay back emf
RE: Diode supression of relay back emf
I am using a 12V relay to operate a DC motor in a motorcoach. I was wondering how important it is in this application to use back emf supression diodes across the relay coil.
///Not necessarily back emf suppression diodes across the relay coil. The suppression resistors are most reliable and least expensive.\\\
Do I really need to care about the energy spikes being put back on the 12VDC supply line?
///Yes, actually about voltage spikes that contain some energy. However, the voltage spike is actually detrimental.\\\
I had already put them in my circuit as a "sure, why not" but then realized that I now need to add a full-wave bridge to protect against reverse input polarity. I would like to drop the relays and the bridge if they are not really needed.
RE: Diode supression of relay back emf
http://relays.tycoelectronics.com/app_pdfs/13c3311.pdf
for suppression techniques and hardware
RE: Diode supression of relay back emf
There is another consideration that should be taken into account if suppress the relay. Doing so will slow the relay’s drop out time. This will reduce the life of the main contacts due to increased arcing and may affect the applications performance.
A balance can be achieved by using a diode in series with a resistor that are connected across the coil terminals.
Regards,
RE: Diode supression of relay back emf
RE: Diode supression of relay back emf
True, but does Megshurts want to be messing about with springs?
If he does, he may have a problem with relay's operating characteristics i.e. pull-in & drop out voltages.
Regards,
RE: Diode supression of relay back emf
prevent magnetizm build up in the relay with heavy duty cycle.
RE: Diode supression of relay back emf
RE: Diode supression of relay back emf
RE: Diode supression of relay back emf