Problem with relays

[Nickman4456]

Recently I've been working on a circuit with a relay. I got the circuit to work, but then it broke. I think I've narrowed the problem to the relay, which is a DPDT (double pole double throw) relay. When the relay is magnetized, electricity doesn't seem to travel through the pole and the lead it's supposed to be touching when moved (due to the electromagnet pushing it away). Is this a common problem/ has it ever happened to any of you? Any suggestions to fix the problem? Thanks

[kmusa]

More detail about what you are trying to do, and how you have things connected would be useful.

-Karlis

[SuperBK]

If you are using your own relay, and not a spike, be sure to put a diode across the coil in the opposite direction of the turn on current to clamp excessive voltage. without that, it could damage components which would lead to intermittent behavior.

[tStano]

Also, if you're using your own relay, it is considered a CUSTOM CIRCUIT so you can't run a motor off it.

From the manual

R44:
CUSTOM CIRCUITS shall not directly alter the power pathways between the ROBOT battery, PDP, motor controllers, relays,
motors, or other elements of the ROBOT control system (items explicitly mentioned in R55). Custom high impedance voltage
monitoring or low impedance current monitoring circuitry connected to the ROBOT’S electrical system is acceptable, if the
effect on the ROBOT outputs is inconsequential.

R41

The only power regulating devices for actuators permitted on the ROBOT include:
A: Motor controllers
B. Relay Modules
A. Spike H-Bridge Relay (P/N: 217-0220 and SPIKE-RELAY-H)
C: Pneumatics control module

I can't get the indentation right, but it says that the only relay that can be used to drive actuators is the purchased spike.

[Nickman4456]

Originally Posted by SuperBK

If you are using your own relay, and not a spike, be sure to put a diode across the coil in the opposite direction of the turn on current to clamp excessive voltage. without that, it could damage components which would lead to intermittent behavior.

Couldn't the reverse-biased diode completely stop the relay from becoming magnetized (it's a low voltage relay)?

[kmusa]

Originally Posted by Nickman4456

Couldn't the reverse-biased diode completely stop the relay from becoming magnetized (it's a low voltage relay)?

Since most/all of us are assuming that this is a DC relay that you are using, the diode isn't conducting when you energize the relay, so no.

The diode is there to dissipate the energy stored in the relay coil when you stop supplying power to the relay.

[FrankJ]

The relay output lines can only source 7.5 mA @ 5V. Make sure your relay meets that spec. As others have said, if it is not a spike it cannot control anything that moves.

[Mr V]

Can you post the part number for the relay? If it is an automotive type relay the common ones require 200ma to energize them. So with a supply that can only provide 7.5ma you'll never get a strong enough magnetic field to cause the relay to change state.