Eyeeye Robots Hints and Tips Solenoids

Do relays and solenoids, operate slower with a back emf diode? Yes!

Circuit click on it to get a better image

The test set up.

The Circuit

On release of the switch the transistor powering the relay switches off, at the same time the second transistor starts the timer. The timer is then stopped when the normally closed contact of the relay relaxes into the closed position.

The tests

We did about fortyfive runs without, and about fortyfive with, the diode. The results are as follows:-

Results

	No Diode (Micro Seconds)	With Diode (Micro Seconds)
Mean Duration	1676	16391
Std. Dev.	2.2	17.6

Conclusion

The relay magnetic field collapse is slowed significantly by the diode.

Copyright © Ian Inglis, 1998-2003. All rights reserved.