Instructables

Building a switch to invert current

I got a small electrical engine the other day, and I have to hook it up to two switches so that one switch starts the engine clockwise and the other counter-clockwise. My initial thought was to simply hook it up to two separate batteries each with a switch and one with the current reverted (like illustrated). But I'm wondering if there's a better way to go about this. For instance I have no idea if accidently activating both switches simultaneously will blow up the engine :s

Picture of Building a switch to invert current
Jaycub5 years ago
Don't worry, if you turn on both switches in this circut nothing bad would happen to the motor. It would just be shorting-out the batteries in series.
comodore5 years ago
What you need is an H-bridge, that's just the thing used in toy cars, so it can go forward and reverse.
Here is an Instructables on how to make it.
http://www.instructables.com/id/How-to-make-an-H-bridge/

Hope it helps! :D
Flark (author)  comodore5 years ago
This does look like exactly what I need :) thank you for the suggestion (thanks to gmoon also).
comodore Flark5 years ago
ok, just trying to help. :D
more about transfer switch
what? :)
Tanners5 years ago
well you don't have to use 2 batteries but yea that seems like the easiest thing to do and my advice would be don't put both switches on at the same time i don't know what will happen but it probably isn't good for the motor.
Padlock Tanners5 years ago
(removed by author or community request)
Padlock Padlock5 years ago
(removed by author or community request)
Padlock Padlock5 years ago
Ignore the schematic I made above, if you already read it. It doesn't work!
Flark (author)  Padlock5 years ago
That's fine. Thanks for the help :) I've done a temporary solution like the one I sketched but will look into the H-bridge for the final solution
gmoon5 years ago
You might search on instructables (or elsewhere) for H bridge, there are several examples...
Flark (author) 5 years ago
Thank you for the suggestions. I do need the two switches to be separated though as they need to be pressed in two physically different locations, so I'm not sure if the DPDT-switch would work. I've found some schematics for DPDT switches, so will look into those to see if the logic can be transferred into something home-made. Again, thanks for the suggestions :)
you can do like this. youll need 1 dpdt (6 entries) (simple 2 state one without center off) and 1 simple switch (2 entries) each switch makes the motor work in 1 direction when both switches are on the motor just defaults to 1 direction if you want it to be off when both are on you need spdt (3 entries) instead of the simple switch
motor.png
. You can use two DPST switches, but you will lose the "interlock" feature (you will be able to close both switches at once). . The wiring is much simpler than it appears at first glance. You just have to look at it for a while. The X that BinaryBoy mentions is what swaps polarity. . If you are familiar with house wiring, a three-way switch is a SPDT. Glue two 3-ways together (and bond the toggles together) to get a DPDT.
110100101105 years ago
do what NM said

the switch comes with 6 entries. connect the corners with the opposite corners in like X. connect 2 wires from something A to the 2 wires of the X. connect 2 wires from something B to the 2 center entries on the switch

it does not matter if A=battery B=motor or the other way

for your second question : motor wont get damaged. batteries yes and possibly wires and switches yes too
NachoMahma5 years ago
. You can do it with a DPDT (double-pole, double-throw) switch. If you want to use the same switch to turn the motor off, specify "center off" (so that would be a DPDT with center off switch.*

*Not a recommendation, just close to the top of the search results.