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Radio-Controlled Vehicle made from Cordless Screwdrivers
What This Is
This is a radio-controlled vehicle made from two cheap, cordless power tools with wheels attached. The electrical control part consists only of an old R/C controller, two servos, and 4 microswitches. Since I had most parts already in my part bins, it cost me about 20$ to build.
When I first saw cheap cordless screwdrivers, I started to think about (mis)using them for a purpose like this. A self-contained gearmotor with rechargeable power supply with a socket for attaching anything you wanted seemed perfect for a small vehicle or robot base. Not to mention far cheaper and easier than rolling my own.
So I decided to make an R/C car out of two screwdrivers to see how workable it would be. And while I was at it, I resolved NOT to use any fancy motor driver electronics or anything. It can drive and steer without electronic drive motor control - it uses switches only. It worked great.
Why This Is
This was just a fun experiment in making a wheeled vehicle that used 10$ cordless screwdrivers as the motors and simple switches as the motor controls. Screwdrivers provide tons of power, are self-contained, reasonably small, and cheap! Thanks to some fortunate contents of my part bins, I didn't need to buy anything other than the screwdrivers - but even if I had had to buy everything it wouldn't break the bank. The fanciest part is the R/C unit - which is also from my parts bin and is over 20 years old at this writing; not particularly valuable or specialized but it works just fine.
This project shows that even with no speed control and simple steering, there is a perfectly usable amount of maneuverability with the simple drive system (depending on your application, of course). It would be useful as either a radio-controlled vehicle (like I made) or as the base of a Wheeled Robot. It won't break any speed records but the screwdrivers provide loads of torque and they are self-contained with built-in recharging plugs.
The exact parts are not very important - the basic design is more useful for anyone attempting to make one of their own; but here are the basics of what I used:
The cordless screwdrivers had their switches removed, and wire leads were put in place. 4 wires came out of each screwdriver: 2 for the motor leads, and 2 for the power supply (+ and -).
Applying the extended power wires to the extended motor wires runs the motor directly.
A stiff base is needed to support the screwdrivers. I attached them with thick zip straps. If I were to do it over again, I would put the thick fastener part of the zip ties on the TOP of the unit to get an extra few millimeters of ground clearance (though your clearance ultimately depends on the diameter of your wheels).
DRIVE CONTROLS (STEERING AND MOTOR CONTROL)
The vehicle moves forward when both motors are turned on, and turns by shutting off one of the motors. Left motor shut off to turn left, right motor shut off to turn right. This functionality is basic, but effective. The biggest drawback is that there is no ability to reverse (though it could be done by adding more switches and possibly at least one more servo.)
This is all simpler than it sounds. The servos are arranged with the microswitches such that each servo (one for FORWARD/STOP, the other for TURN DIRECTION) pushes two microswitches with the servo's arm - one switch per side of the servo arm. The result is that one servo controls FORWARD/STOP by holding the switches closed (STOP), or releasing them (FORWARD). The other servo controls LEFT/RIGHT/STRAIGHT by pushing one or the other of the remaining switches, or neither.
MOUNTING DRIVE COMPONENTS
I opted for strapping on the receiver and battery pack with velcro strips, and gluing servos to the screwdriver body with hot glue. I tied excess wires in a bundle with a strip of velcro strap.
The wheels came from a broken toy truck. I took sockets from the socket and bit set the screwdrivers came with as the interface to the screwdriver, and attached the wheels to it. I used a wood screw and an expanding drywall anchor at first to provide a simple friction fit, but later strengthened it by gooping on some 5-minute 2-part epoxy on the joint.
FINISHING TOUCHES, AND TESTING
The antenna on the R/C receiver is just a wire, and I lacked a thin plastic tube for it so I just attached a piece of plastic cut from some packaging. A thin dowel would have been better (and far less ugly), but I couldn't locate one. Such are the pitfalls of being determined to use only the contents of a junk box.
Once the screwdrivers are charged and any glue has cured or dried, the vehicle is ready to roll! Power up the R/C unit (both receiver and transmitter) and you're ready to go.
One thing you will probably notice is that the torque of the vehicle is limited by the grip of the tires. Even cheap electric screwdrivers are capable of delivering quite a lot of power -- easily enough for your vehicle to drive itself up the steepest of inclines as long as the wheels you use have enough grip.
Another thing that was apparent to me is that even though the screwdrivers were independantly powered and isolated from one another, I had no problems with "drift" in the steering due to one motor running a little faster or slower than the other. Also, steering by stopping one motor or the other was a perfectly serviceable method - and it was much simpler than steering by physically turning the wheels or motors.
Finally, the lack of a reverse could be a problem when you ran into something. Adding a reverse would be possible, but would require adding more switches and possibly an additional servo. The requirement for a reverse circuit could be the tipping point in complexity, where it becomes worth it to use electronic motor drivers rather than deal with the increased number of switches and wiring required to add it otherwise.
I think there's excellent potential in using cordless screwdrivers in this way (or a similar way) as the base for an R/C vehicle or possibly also Wheeled Robots.
Tracked vehicles would be particularly well-suited to using screwdrivers as their drive systems.
I stuck a camera onto the "steering" servo to test an idea I had. I wanted to know if it was easier to remote-pilot an RC vehicle if the camera looked "into" a turn, like you do when you steer a car. (Most cameras stuck to RC vehicles simply look straight ahead.) I think it has great potential.
Here is a link to a Google video attempting to demonstrate this concept.
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