Let's Make Robots!

RC receiver help

Hello all.


I have a controller and RC board from an old rc car with tank style steering. I was playing around with getting it to control one of my bots, but i cant seem to get the wiring right. I'm pretty sure that i have the wires to the motors right, but i think i may be missing a wire. i can only get one wheel/tread to go in one direction at a time. There are four wires that correspond to 2 different points on the controller board. if i remember right, i am the one that soldered the wires. MB1, MB2, MA1, MA2. Then there is a VCC2, and a Ground. 


I think the VCC goes to the battery pack, the ground to the battery pack, and the other 4 go to the motors right? Shouldnt there be some sort of power conrol that taps into the battery and ground lines? I know that i can make this work, i just cant figure out what im doing wrong! I am including some pics of the board. the red and black wires are all soldered to the connections mentioned above. someone Please please please help. I know its something stupid and its driving me insane!





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I was planning on turning a RC car into an autonomous/RC vehicle I was only going to connect a uC to the appropriate pins on the RX2 chip to control the vehicle.

To my knowledge, it should all work the same, but its been a few years since i gutted it. I wa never intending on using it again so i wasnt gentle with it. My thinking is that i ripped another wire clean off. I'm fairly positive we havent lost any magic smoke, as you put it. i think the thing is sound... its a matter of tweaking the wires and such. on an h bridge, shouldnt there be a pwm wire and ground or something like that? (sorry, most of my experience has to do with arduino, so im basing off of that)

For control, there has to be a common ground.

When I hack RC toys, I usually use a 5V power source, find the ground to the toy and hook that up to my 5v common.  Actually, again the first thing I do with a working RC toy is to take measurements in the different states. 

For example, when it is turning left, I'll take measurements on suspected control lines and compare that to the reading I took when the thing was at rest.  Map out all the states (stop, right forward, right backwards, left forward, left backwards).  Then you know exactly what it needs to do what.

If it is a four transistor NPN H-bridge - you can find how to control with this instructable  http://www.instructables.com/id/H-Bridge-on-a-Breadboard/ 

You want to avoid shoot-through.

Hope this helps. Good Luck


Wikipedia to the rescue !  http://en.wikipedia.org/wiki/Magic_smoke 

Was wondering the possibility of it being damaged.

When I hack a RC toy, I usually take readings with the multi-meter before soldering.  What you have done seems reasonable to me, did you test the values before soldering?

I think VCC2 is usually for motor power... So you're using the remote and nothing happens?

Is there any way you can put it in it's original state to verify that its working as intended? (You know to verify the magic smoke is still inside)



Forgive my total noobish understanding of the language... magic smoke?


Yes, I have a multimeter.

From what I can see it looks like it might be a NPN H Bridge like this http://letsmakerobots.com/node/9450

My next question would be - is there any magic smoke missing?  

Do you have a MultiMeter ?  (If not you should get a MultiMeter)