choosing Relay ratings and battery

Thread Starter

anabya

Joined Mar 19, 2016
1
Hello,
I'm stuck in my project where i need to choose a relay that will work as a:
- switch to turn on (two heating pads each with 600mA, 5 volts )
- and another relay to switch ( four fans each with 0.3A 5 volts).
So i am stuck with the ratings of the relays because am not so familiar with relays.
So according to the relays i will buy the specific battery for these (it would be a rechargable battery), so if you can recommend the ratings as well.
Also the relays are connected to arduino which's powered by a 3.7v LIPO battery.
Note: both relays are connected to one battery and the resources would be connected in parallel !
I would appreciate your help..
 

Reloadron

Joined Jan 15, 2015
4,591
You need to start with your ARDUINO PIN CURRENT LIMITATIONS and work from there. Since you plan to work with relays the next step would be finding suitable relays. With the relays you need to look at the relay coil both voltage and current making sure you are within your previous limits for the Arduino IO pins. Should this not work well it may be necessary to have the Arduino drive the relay coil using a transistor or similar. A simple Google of "Arduino relay driver circuit" will bring up a few dozen hits. That done your relay contacts will also need consideration as to the current they will need to handle for your loads as well as allowing some overhead. For example your fans will require 4 X 0.3 Amp or 1.2 Amp total so you want contacts capable of 1.2 Amps plus some overhead so figure 2 Amp contacts approximately.
Your battery choice will depend on how long the battery needs yo last. Your heating pads you mention 5 volts as well as the fans, what is the power source for heating pads and fans? Actually I would also use as was suggested MOSFETs, Logic Level Mosfets for heater and fan control.

Ron
 

LE-BU

Joined Nov 3, 2017
18
Hello,
I'm stuck in my project where i need to choose a relay that will work as a:
- switch to turn on (two heating pads each with 600mA, 5 volts )
- and another relay to switch ( four fans each with 0.3A 5 volts).
So i am stuck with the ratings of the relays because am not so familiar with relays.
So according to the relays i will buy the specific battery for these (it would be a rechargable battery), so if you can recommend the ratings as well.
Also the relays are connected to arduino which's powered by a 3.7v LIPO battery.
Note: both relays are connected to one battery and the resources would be connected in parallel !
I would appreciate your help..
Hello , you can use this one , be careful , the max voltage for the coil is 120% of 3V --> 3.6V . Use a Zener diode if necessary.

upload_2017-11-7_22-34-39.png
 

LE-BU

Joined Nov 3, 2017
18
Be careful about the coil current , for this one is 166 mA . Arduino output is 20 mA . You must insert betwen the arduino an the coil a bipolar transistor
 
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