Newbie here. Need help lowering current draw across relays.

Chris's picture

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Joined: Nov 08, 2020

Replies: 1
Newbie here. Need help lowering current draw across relays.
November 8, 2020 - 7:02pm
Chris's picture

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Joined: Nov 08, 2020

Replies: 1

I designed and built an Alexa powered automatic chicken coop door opener.  I am using an Eachen wifi inching module, a forward/reverse relay module, and a 12v actuator all of which I got of Amazon.  My current design works well, but my current draw is draining the battery down much too quickly.  I was planning on using a 12v 7.5ah battery meant to be used on broadcast deer feeders.  It didn't take but about a week to run the battery down.  

I under estimated the amount of current required to keep what is effectively 2 relays engergized all the time.  

I have done a little research and have come to the conclusion that I could add a capacitor and a resistor and cut the current requirement to hold the relays open effectively increasing my battery life that way. The source I read described measuring the resistance accross the relay and matching a resistor to 1/3 of that reading, and adding a 1000uf capacitor to the circuit.  From what I understand the capacitor would charge as the relay is switched on and the resistor would allow the capacitor to hold the relay open at the predeteminded 1/3.  I am by no means an electronic guru, I am merely a novice experimenting here.  Will this work?  I don't even know how measure the Eachen's current draw since it's all on a module.  I am not sure where to start.

 

Is there a better choice of component?  I need a module like the Eachen to interface with Alexa. Is there another way to switch polarity and let the Eachen carry the load and eleminate the second relay module? All I have the Eachen doing is opeing and closing either the NC or NO sides of it's output and using that to switch the momentary inputs on the F/R module.

  Considering I have never done anything like this before and I am not a very creative person, I am quite proud of it.  I have been using it for several weeks and it works flawlessly on grid power.  I have tons of people on FB wanting me to sell these.

I tried to post a picture, but every time I click on the image button and add a url and comem back it wipes out my text. I have retyped this twice now.

Sourav Gupta's picture

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Joined: Feb 12, 2018

Replies: 696

Well, I dont think this will be at all effective. Relays draws current, the capacitor will also be charged using the same battery. Thus whether it is battery or capacitor, energy will end up coming from the battery. One major changes that can be done in your design is to removing the relays and using a transistor or MOSFET based solution. But that will became advanced and complex task for you.

Other good solution is to replace those relays using solid state one. Maybe it will work. Could you share the relays spec? do not paste URL. Try the IMCE button on the tab for posting the image. It is  situated just beside the left side of the IFrame (Globe symbol).