Controlling voltage input to relay

Thread Starter

Brad Fowler

Joined Oct 14, 2020
4
I am currently using an Altronix RBSN 12VDC relay to trigger an input on another system. The output to the relay has a constant 3V DC and sometimes up to 6V DC and increases to 12 VDC when in alarm. This is causing issues because the relay will at times, randomly change states or if triggered, the relay will hang on the voltage that is present. What would be the best way to allow only 10-12 VDC to the relay? A cheap off the shelf alternative would be preferred, as I am not that well versed in electronic components. Any help would be appreciated.
 

eetech00

Joined Jun 8, 2013
2,043
I am currently using an Altronix RBSN 12VDC relay to trigger an input on another system. The output to the relay has a constant 3V DC and sometimes up to 6V DC and increases to 12 VDC when in alarm. This is causing issues because the relay will at times, randomly change states or if triggered, the relay will hang on the voltage that is present. What would be the best way to allow only 10-12 VDC to the relay? A cheap off the shelf alternative would be preferred, as I am not that well versed in electronic components. Any help would be appreciated.
Please post a schematic of your circuit.
 

Tonyr1084

Joined Sep 24, 2015
5,238
Many relays have a pull-in value and a drop-out value. So a common 12V relay may require 70% of 12V to pull in and hold the relay in the energized position down to 30% of 12V. These numbers are not hard facts, just common approximations of how relays work. I've bench tested several relays to see what their pull-in values are, then drop the voltage till the relay drops out. These were the approximate numbers I came up with.

What voltage do you want the relay to trigger?
What voltage do you want the relay to drop-out?
 

Thread Starter

Brad Fowler

Joined Oct 14, 2020
4
10-12 Volts to trigger
l would like it to drop out below 10 volts

The relay is is coming off an output on a wader management controller. the NC outputs are used to give a dry trip to another device on a nurse call system.
 

Tonyr1084

Joined Sep 24, 2015
5,238
The relay is is coming off an output on a wader management controller. the NC outputs are used to give a dry trip to another device on a nurse call system.

A cheap off the shelf alternative would be preferred, as I am not that well versed in electronic components.
The mention of "Nurse" suggests a highly reliable circuit will be needed. I hesitate to offer any further advice given the nature of human life and the possibility of harm to another human from a failed system. That's my honest opinion.

To truly be able to give you a much better answer than "simple and cheap" we will need to know a whole lot more about HOW it is going to be used, with WHAT it is going to be used, WHAT the parameters are (controlling circuitry as well as dependent circuitry) and probably a few more things I'm overlooking.

One critical part of the build is your competency. Can you build circuits? Complex circuits? Sensitive circuits? - Eh, there's a lot more to this than meets the eye now that you mentioned nurses.
 

Thread Starter

Brad Fowler

Joined Oct 14, 2020
4
I get it, that's why I was asking for an off the shelf product. This is a matter of making two different systems communicate. The wander management controller initiates an alarm and triggers an output to light an LED. We are jumping on that output and installing a relay to trigger a nurse call system with a dry trip. The circuitry involved in both components is well above me, I only intend to use the provided inputs/outputs on each system.
 

sghioto

Joined Dec 31, 2017
1,556
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