Hi all,
Thank you Guenther for your relay overview !
Something to take in account with when designing circuits !
The test results of the RWO relay :
There is no diode in the module 😯
First of all, I measured the coil resistance which is about 70 Ohm like Guenther mentioned.
Then I set up a simple circuit : battery – 120 Ohm resistor – switch – relay. I used my oscilloscope on single trigger and measured the fly back pulse across the relay coil when operating the switch.
Indeed, we have spikes up to 40 Volts. So, by adding an external diode across the coil, this spike was completely suppressed.
Uh oh, we really need this diode to protect our semiconductors …
Is this a coincidence ? As far as I can see, there’s no place where it can be soldered on the PCB.
Can someone check with their relays ?
I hope I have warranty on this …
Greetings