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how do you make a voltage splitter to dividea current in two so they act as if they were coming from different sources

hello, i am building and rc tank that uses 4 relays to power 2 motors in both forwards motion and backwards, all running from 1 battery pack. however ive hit a snag in my developements in which the single battery pack was actually bypassing the relays as it connected to the terminals of the motors, therefore not allowing me to use one relay to apply +/- power the motor via the battery and useing another to apply -/+ via another. my only logical solution at the time was to remove 1 of the 3 battery packs being used (were each batpack contains 10X1.2v 3AH AA batteries), and arrange it so that 1 pack powerd the motor when going in reverse, and the other two were to power the motor going forwards, and although this means that my tank would run fine, and the subtraction of 1 pack doesnt make a difference power wise to the motors as they run at max efficiency with 2 packs, its still a real hassle to recharge them as i cant just charge em all up at once, the reverse motor battery pack may run out before the forwards, and vice versa, giving me less time to run the tank, than if they were together.
so now you know my problem, what i need is a solution, how can i make a voltage splitter or current splitter or whatever, so that it can divide a current in two so that if i were to connect a positive wire from current 1, and negative wire from current 2 it would not complete a circuit, and basically act like they come from two totally different sources. this was what i was doing until i realised that when i tested the motors in either direction, it was actually going forwards each time i switched it on, after swaping the wires around when it would just run the motor if the relays werent even turned on. my tank has nothing yet on its motors shafts like gears or nothing, it was a simple mistake.
so please, can anyone help me?

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orksecurity6 years ago
It sounds to me as if your problem was that you were trying to reverse the motor using a single-pole relay connection, whereas you actually need a two-pole connection (DPDT)... you need to exchange the two wires running to the motor, not just move one of them.
oldmanbeefjerky (author)  orksecurity6 years ago
right after re-reading your post , i think i misread what you meant.

does this crude diagram i just drew represent what you meant by changing both wires?
in this, the thing with the +/- sign would rotate , conecting the wires with the motor terminal when they hit it, and in reverse, they would swap terminals, thus rversing the motor!.
i could run something like that simply off of the receiver, but i would still rather try the simpler solution of using a current splitter, as my recievers and everything has been mounted permanently, and the kits are quite expensive.
switch.png
Double-pole, double-throw relay.

When coil is off, input A is connected to output A0 and input B is connected to output B0.

When coil is on, input A is connected to output A1 and input B is connected to output B1.

Then all you need to do is connect A and B to power, A0 to B1 and one side of your motor, and A1 to B0 and the other side of your motor. With relay on, motor runs one direction; with relay off, it runs the other direction.
Note that this doesn't require two separate power sources.

DPDT relays are commonly available and cheap.
oldmanbeefjerky (author)  orksecurity6 years ago
http://cgi.ebay.com/Two-DPDT-Signal-Relays-Module-Board-12V-8051-PIC-/130426272824?pt=LH_DefaultDomain_0&hash=item1e5e02fc38

would these be suitable, also are thay actually two seperate dpdt relays on one board, or are they two normal relays that act like a dpdt relay?
because from what i have read, these match what i need perfectly, as thge relays need to be switched by a 6v 700ma current, from my receiver.
oldmanbeefjerky (author)  orksecurity6 years ago
hmm, i just did a bit of research and still am a bit unclear......
however, i do have something i could relate to this. you see once i did some work on rebuilding a small childrens ride-on electric car, however the gear box that determined which direction you went was broken, so i rewired the car to instead use the cars on off switch , which had 3 terminals in two sets, for a total of 6 terminals, to change the polarity of the power going to the motor
example

[] []
[] []
[] []

do these dpdt relays work in the same way?

you see there was something i didnt quite understand about what you said, which was how you said that one switch would always be on, and one would always be off, so the idea im getting now is that if no signal is going to the relay its off, which means that the motor will be turned on, im just a little confused is all.
oldmanbeefjerky (author)  orksecurity6 years ago
so if i got two, i could use the relays i already have to power these extra relays, right?
oldmanbeefjerky (author)  orksecurity6 years ago
yes, in actual fact i realised this right after posting this question!, i would need tworelays instead of one, so that the battery could not do anything at all while the relays were shut off, however, i cant do that with the resources i have and my little money shortage right now. also the wireing is perfectly fine, but i cannot give an exact diagram of it, as i have like 2m of wire in it, but i will give you a crude drawing in paint of how just one of the motors is connected

this is how it is currently set up, the larger box shows how the relays are linked to the receiver, its basicaly all that needs to be shown.
previously, i tried doing this with all the battery packs together, and using dioded to, do what i hoped, was prevent this issue.

right now though, i am not prepeard to add more relay cards (as they are relay card sets), and the board i have the relay cards mounted on has not got any more room anyway, all i can see working for this would be to have a sort of current splitter that would "act" as the second battery pack, while being supplied by only one pack so i get a longer performance from the tank.
more relays, or different relays are out of the question!
cheapdiagram.png
lemonie6 years ago

Your wiring is wrong. Can you give us your circuit-diagram?

L