12V bus and relay control

Post Reply
User avatar
joshlawless
Posts: 138
Joined: Thu May 23, 2013 2:52 pm

12V bus and relay control

Post by joshlawless »

I have a lot of 12V AC-DC power supplies connected to tank hardware -- one for a Reef Octopus DC skimmer pump (which, though it shares the same form factor as the Jebao, unfortunately doesn't work with the Jebao harness), two for Jebao DC return pumps, one for a filter manifold DC pump, other smaller wall-wart types for various Reef Angel expansion modules (2x 16 channel PWM), one old laptop power supply for ventilation fans, etc. etc. etc. Some of these are controlled by relays (the skimmer), but most are powered on all the time (with some relying on PWM signals to turn off, like the return pumps).

I thought it might make sense to obtain a larger (but still fanless) 12V power supply (like this one at Amazon), and use it as a 12V power bus for all the 12V devices (except those needing galvanic isolation, like the ORP expansion, and the Salinity expansion). This would reduce clutter, waste heat, and if a higher-efficiency power supply, electrical power.

This would be easy enough for those devices that don't require independently addressable on/off control, but for those that do (like the skimmer), it would be nice to be able to connect them to the bus with a relay and control the relay from the Reef Angel (either through the ATO pins, or the I/O module, or even the 12V Power Control Expansion module).

As I understand it, the ATO pins could only be safely connected to a relay with a very low coil current, but I wonder if the I/O module could generate more? As a last resort, the 12V Power Control Expansion module can generate 500mA per channel (and could itself draw power from the 12V bus), which should surely be enough even for a cheap automotive 12V relay?

Has anyone done anything like this? Does anyone know of a 12V relay with a very low coil current that would suffice to power a 2.5A 12V Reef Octopus skimmer pump?
User avatar
joshlawless
Posts: 138
Joined: Thu May 23, 2013 2:52 pm

Re: 12V bus and relay control

Post by joshlawless »

Also, for those devices that would benefit from reduced power (e.g., ventilation fans), would this kit be appropriate for using the 5V PWM output of a dimming channel to reduce the voltage going to a device?

https://www.sparkfun.com/products/12959
User avatar
Sacohen
Posts: 1833
Joined: Sun Apr 21, 2013 6:25 am
Location: Davie, FL

Re: 12V bus and relay control

Post by Sacohen »

joshlawless;

The Jebao pumps are 24V if I remember correctly and I'm guessing that your Reef Octopus DC skimmer pump is too. \

The 12V Power Control Expansion has a limit to the amount of amps it can handle. I believe it it 500ma.
User avatar
joshlawless
Posts: 138
Joined: Thu May 23, 2013 2:52 pm

Re: 12V bus and relay control

Post by joshlawless »

D'oh. Right you are -- 24V. Still, replacing four 24V bricks with one power supply has _some_ appeal (admittedly, not as much).
User avatar
joshlawless
Posts: 138
Joined: Thu May 23, 2013 2:52 pm

Re: 12V bus and relay control

Post by joshlawless »

It looks like this $8 relay board might still fit the bill: Amazon link

Image
  • 5V 4-Channel Relay interface board, and each one needs 15-20mA Driver Current
  • Equipped with high-current relay, AC250V 10A ; DC30V 10A
  • Standard interface that can be controlled directly by microcontroller (Arduino , 8051, AVR, PIC, DSP, ARM, ARM, MSP431, TTL logic)
  • Indication LED's for Relay output status
Post Reply