Let's Make Robots!

Relays (DPDT)

Vendor's Description: 

Relays are an alternative to motor-controllers.

They do consume a little power from your battery when in either on or off position (turned on) - but they also do deliver the full power that you want - where a motor-controller often takes some of the power (voltage-drop).

They can be found to be able to handle much more current than a motor controller matched in size (and price).

They are "slow". That is; You can not do PWM with them (Slow the motor down by just giving it pulses) - but then again you can, if your robot has a little inertia (is moving forward) - then the on/off speed of the relays is way fast enough to slow down / drive half speed etc.

They can be found in a million configurations.

One very common and useful is a standard 5V DPDT relay that can be found anywhere. 2 of those can make a motor reverse / turn on / off.

Here is a fantastic article on how to work with them

Also check out this little robot. And these.

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Probably worth mentioning latching relays here for those who don''t know about them.  I used one on THIS project.

A latching relay has two coils and the contacts can be toggled from one state to the other by pulsing the coils.  The difference is that a latching relay will stay in the state it's in - It's a relay with a memory. 

They're a bit harder to find than standard relays (Farnell do them) but they are worth bearing in mind.


Oh, thanks. i guess that is pretty smart, because they will consume no power then.

So in many ways / in some situations, this will be the best solution, even over motor drivers!