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# 12V DC Diagram that shows a motor reversing on its own? Answered

So I made this moving remote control target system. I used a treadmill Motor to connected to RC car speed controller with a radio receiver. Works good but now I want to up grade I'm new to electronics and have a basic idea. What I want to do is have the motor hooked up to a speed controller and  run till a certain point then reverse. the opposite direction. I know limit switches are incorporated some wear any one have an idea how the diagram would look thanks

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## 10 Replies

-max- (author)2015-11-09

12V brushed DC motors are often reversed by reversing the polarity. (do NOT do this if there is a speed controller. It most likely will let out the magic smoke.) so you may want to consider using a H bridge. Look at the picture below to see how to wire up a DPDT switch to reverse polarity:

http://www.eleinmec.com/figures/012_01.gif

https://en.wikipedia.org/wiki/H_bridge#/media/File...

The second picture shows all four switches in that H bridge, you can see by turning on S1 and S4 will let the motor go one way, while turning on only S2 and S3 will reverse the motor.

With that basic knowledge, it is easy to design something that will imediatly reverse direction when a limit switch is hit.

unshiftedmatt (author)2015-11-09

Thanks ive been reading up on circuits and I think I bit off more then I can chew..I am going to pick up a bread board and see if I can do this on a small scale first. I need a better knowledge at the basics. The speed controller/reciver I have goes to a rugged RC car. It acts as a on off and a H bridge I believe. I can reverse the motor with a turn of the wireless(audio) joystick and increase the speed depending on how far I move the stick. Some how I need make so when the switch is hit the motor will reverse unitll the next switch is hit. I'm looking for a constant back and fourth while retaining my audio control over the motor. That's were I think ICeng is thinking the timing can comin in effect. I have seen this with two leds alternating I think its a 555 Astable circuit?

-max- (author)2015-11-09

So basicly you want to make the RC car bounce back and forth between 2 endpoints. You will need a device that "remembers" which limit switch it had last hit to continue to propel the RC vehicle in the right direction. Luckily, such a device exists, it is called a "latch." a latch does sort of what it sounds like: When triggered is stays "stuck" on, and when triggered again, will stay off. These latches can be made completly mechanically, (a household switch (the actual lever itself) is a very simple example) electromechanically (by use of cluckin' relays, electromagnets, solenoids, etc.) or completly electrically, like in the case of flip flops!

unshiftedmatt (author)2015-11-11

Thanks Max it is intimidating i will take a look at the latch and those channels.. Have you ever seen liner track like in movie production.. The cammar is on wheels and is pushed on the the track with ease. Now imagine it's a steel target the motor is at one end and moves the target via rope run through a pulley at the other end . I control the motor via RC audio reciever . I drew a quick picture down below . It's not to scale I'm looking for about a 30 foot track

-max- (author)2015-11-11

This is an interactive image of what a latch does. If you have some time, build up the circuit and play around with it some! I'm sure you can see the potential in this if you replace some of those resistors with a motor controller and the switches are limit switches!

Below is a video describing how you can use a basic relay as a latch.

-max- (author)2015-11-09

Yeah, electronics were really intimidating when I first got into it, and that was before the internet existed in my world! If you are into learning electronics, I recommend looking at afrotechmods, EEVblog, and electronicsNmore all of which are excellent youtube channels! I have also posted a few project video's and "Tutorial Tuesdays" to get people started in electronics!

rickharris (author)2015-11-11

This is actually much easier done mechanically.

Drive a large wheel with the motor so it runs slowly then fix an arm on the rim of the wheel - the other end goes to the targets on their cord or belt. Thus as the wheel turns the arm will swing back and forth driving the targets

unshiftedmatt (author)2015-11-11

thanks RickHarris I didn't think of that however I'm looking to do a 30 foot track.. But now I have cool idea at making a pivoting target with the crank..

iceng (author)2015-11-08

If you ignore the right side motors of the L293D IC, the left side Motor can be reversed with a 555 timer output pin3 connected both pin-2 and pin-7 and will reverse when it times-out and changes.

Additionally the limit switches will stop the motor if the travel reaches a limit before timeout.

unshiftedmatt (author)2015-11-09

Thank you for responding sadly I'm rather ignorant to diagrams. I understand it somewhat. I have never done anything with circuits besides simple things like fuses and alternators. below is the most ive done . I can use the remote to a increase/slow speed stop it reverse direction. But I would like to set it on auto so when it gets to one side it will go the opposite direction. Depending on how fast the setting is I believe a time limit may not work. Also if it slams ageist the motor or pulling it punts strain on the system.