# controller for a crawler?



## jabberwocky (Apr 30, 2008)

Any good ideas for a "crawler" controller?
Im sure any "tank" controller would work, but Im hoping someones got a good one that will do the job without beaking the bank.

Thanks alot.........


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## hpropman (Jul 27, 2008)

You can use a pair of relays DPDT type to switch the motors on and off and to control direction. A third relay can control the power to make him stop. what exactly do you want him do. do you want him to respond to motion? You can also have him track a light. The easiest way is to use a controller like a prop1 or a stand alone microcontroller like a picaxe or a basic stamp. I am also thinking of making one of these this year. I might use wiper motors though. I might also try to control him using sound with the scary terry tone detector circuit. Just a few ideas floating around in my head


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## bourno (Jan 21, 2006)

I gave up looking for a good toy to hack to have a cheaper way to control the crawler when I volunteered to provide a Make and Take session at IronStock. Each motor of the crawler draws around 3-5 amps and didn't want to spend how many $$ on different toys that might be suitable for the application.

I did buy a couple different Chinese RF remote to provide On/Off control for each motor. I ordered some momentary ON receiver boards. There are some that are selectable for Toggle, Momentary, and Latched.

Hpropman, your idea is interesting with the 3rd relay to control power to the other 2 relays. The first Chinese controller I got was a 4 channel unit, but it only allowed *one relay*  to be active at a time which squashed my idea of a cheap, easy On/Off control.

I did get some 2 channel units which I found that could have one or both of the relays active on the receiver. By using 2 of these units on *different codes* that I could run both arms forward, or both reverse, or run one arm only at a time either forward or reverse. It was not possible to run one arm forward while the other arm ran reverse. The receiver required 12 volts to power it up and think I tried it with the 7.2 volt RC battery pack which would supply the juice for the arm motors, and don't believe it worked at the lower voltage. So would require a separate battery for the receiver power. Not sure if a 9 volt battery worked either properly.

I didn't mess around with it much more as all the people who signed up for the Make and Take went for the dual speed controls that is much easier to wire and control the crawler.

Thought I would pass along any tidbit information that I dink'd around with. Good luck on finding a cheaper alternative as I spent a few $$ on different motors, ESCs, etc that I preferred.

If you do go with the hobby RC route, I liked the Traxxas XL-1 ESCs for the minimum pwm noise when running the motors slow. I used the Vex transmitter (search ebay as I think AllElectronics may be out) and bought the GWS 75mhz r6n or r4n receiver to work with the transmitter. The motors were from Surplus Center, the 12volt, 150 rpm, right angle gear motors LH and RH style. But I ran them at 7.2 volts which worked out great for slowing them down some as the motors were too fast for my taste on 12 volts and easy to find extra battery packs at an RC hobby shop.


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## bourno (Jan 21, 2006)

Over on another forum (maybe the Floridahaunters board), I think one person used a toy truck with a zombie figure over the top of it.


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## Phil (Sep 2, 2007)

I hacked a $10 RC car controller to drive relays in place of the left/right and forward/reverse servos. It provided tank control with independent forward and reverse of the two drive motors. Obviously there is no speed control but it did provide cheap control. For $10 I got the controller and batteries/chargers. I had to add four relays and a 12-volt battery for motor power.


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## bourno (Jan 21, 2006)

Ah, good work with the RC car to relay hack. I like your Power and Control page information and the notebook background.

I assume each relay had a diode in line with the coil as well, so only one of the 2 relay sets could be energized depending on the polarity of the output voltage that would have been going to the motor.

That is a such a simple and great idea. I was too wrapped up in "proportional" control and didn't even think about using relay H-bridges instead to handle the higher current demand.

A good toy for this relay hack would be the older BattleBot toys that were sold a few years ago and most likely on ebay still. They had a transmitter with dual sticks as the toys were tank steer controlled.


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## Phil (Sep 2, 2007)

Thanks Bourno, that means alot coming from you. I did not think to install clamping diodes on the relays, just connected the negative coil terminals commonly to ground and each servo power output lead to its own positive coil terminal.
The transmitter I used had two sticks at right angles (forward/reverse and left/right). The R/L stick always felt clumsy as a F/R control tank.


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## hpropman (Jul 27, 2008)

I would definitely add the clamping diodes they protect the transistors that switch on the relays and the rest of the circuit from Back emf. It may work now but over time it will damage them.


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## Phil (Sep 2, 2007)

I will take that good advice. Is there a general diode to use or method to determine an appropriate value?


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## hpropman (Jul 27, 2008)

IN4001 will handle 1 amp, IN4002 will handle 2 amps and so on. either one will be fine. remember to install them reverse bias (negative "cathode" diode side to the positive relay pin).


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## Phil (Sep 2, 2007)

looks like the coils are rated at 350mA and I have a handful of 4001s. Thanks for reminder!


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## jabberwocky (Apr 30, 2008)

All great advice.............. thanks alot.
As for the the set-up design using the relays and suggested diodes, can you guys post up a suggested wiring diagram for tis?
Thanks again!


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## Phil (Sep 2, 2007)

I mocked up a diagram of my old hack. In an eggnog haze it looks right to me...


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## jabberwocky (Apr 30, 2008)

Super thanks.............


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