How to Make Servo Driven Screwdriver Tool - DIY

All of a sudden my electric screwdriver died, but instead of running to the store I decided to build one. So in today's Instructable I'm building a servo driven electric screwdriver using very inexpensive materials. It doesn't take more than 1 hour to build and you can find all the necessary components from Ebay for under 10$! It's a super simple project so let's start building!

The key component in this system is the servo and that's why I highly recommend a metal gear servo. However, in this video/instructable I'm going to use a servo with plastic gears.

1. Servo:http://www.ebay.com/itm/Micro-9g-RC-Servo-for-Trex...
2. USB cable: http://www.ebay.com/itm/USB-V8-Micro-Data-Sync-Cha...
3. Wire: http://www.ebay.com/itm/1-2-5-10M-Silicone-Wire-Ca...
4. Shrink tube: http://www.ebay.com/itm/Heat-Shrink-Tube-Shrinkabl...
5. Power bank: http://www.ebay.com/itm/Power-Bank-Backup-External...
6. Switch: http://www.ebay.com/itm/301953835161?_trksid=p2060...
7. 7mm socket: http://www.ebay.com.au/itm/CR-V-Metric-Hex-Socket-...
8. Connector: http://www.ebay.com/itm/20-Pairs-Micro-JST-1-25-2-...

Begin with disassembling the servo by removing the four screws on the bottom. In order for the servo to continuously rotate we have to remove the mechanical stop from one of the gears (plastic piece shown in second picture).

Pull out the guts and use a plier to get rid of all the electronics inside the servo. A servo works by a motor, controller, potentiometer and a gearbox working together. However, we only need the motor and gearbox.

To easily reverse the rotation of the screwdriver we need to solder a pin connector. This will make us able to reverse the polarity (reverse rotation) by rotating the connector 180°, this will make better sense later in the build.

Solder longer wires and add shrink tubing to any open joints. When this is done you can go ahead and assemble the servo. Add shrink tubing to the connector as well!

Take the USB cable and cut it to a suitable length. Inside you will find 4 wires (green, yellow, black and red), cut away the green and yellow, as we only need the 5V output power (black and red).

Solder the black wire from the USB cable to one of the pins on the electronic switch. Cut a small piece of black wire and solder one end to the middle pin on the electronic switch. Take the other end of the black wire, the red wire from the USB cable and solder it to another pin connector. The result should look like picture number 4.

Glue the servo using a moderate amount of hot glue to the power bank. You can also go ahead and glue the switch to a comfurtable posistion. Connect the USB and give it a try.

Your servo will most likely arrive with a couple accessories, also called servo horns. Use the circular and screw it down with a little loctite. When glueing the socket extension you can go absolutetly crazy with the glue. Don't hold back! Though make sure it's center, otherwise you might get wobbling results.

You are now completly done with your very own electrical screwdriver. Unplug and rotate the pin connector in order to reverse the rotation of your screwdriver (picture 2). Obviously a plastic servo won't hold up as good as a metal gear servo, however, mine is still working fine.

With a large powerbank you will be able to use it for many hours before you need to recharge. Even though the servo screwdriver is not quite strong enough to handle the larger screws, it still worked great with the smaller ones.

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