Image 1. The IGO as seen in the store.
This article details hacking the IGO Mini Screwdriver for use in small robots. Inside the IGO is a DC motor, 5 stages of gearing, two screwdriver bits, and 2 AAA Eveready batteries.

I found the IGO Screwdriver at Fry's in Renton (Seattle) Washington. The package allows you to try it, and the torque was strong for such a small package, so I immediately thought about hacking the motor and geartrain for small robots.

The kicker for me was the price. Normal price was $5.99, which was good, but it was on sale (12/12/2003) for $2.99. I bought 2, used one to open up the other, and determined that yes, it is easy to hack. I then went back and bought 10 more.

I also researched the IGO screwdriver on the web. It was just released (December 2003) and is sold through many drug stores or hardware stores for $6 to $10.

Here's the IGO Mini Screwdriver before hacking. It makes a nice bench-top screwdriver but I think I'll find better use for it in robots.


Image 2. The IGO before hacking.

After playing with my new screwdriver for a while, I got serious about opening it up...


Image 3. Backside, screw hole, and batteries.

To open the case we must:

  1. Remove the battery-cap and the batteries. Just twist and remove.
  2. Remove the front cap. This is the hard step, see details below.
  3. Remove the 2 phillips screws.
  4. Pry the case open.

Removing the front cap:

As seen in Image 4 below, the green cap is held in place by 2 tabs that fit tightly in the 2 slots on the sides of the main case. I was able to remove the cap by prying a small slotted screwdriver under the cap and disengaging one tab at a time. The case and the cap are plastic, and I gouged them a bit. You can mangle the cap since you probably don't want to put it back on. I hacked two of these. The first one I actually cut the cap off. The second one, knowing where the 2 tabs were, was much easier to get off.

Once the cap is off, and the 2 screws are removed, the case can be pried open. It is a bit tight since the case is aligned using 3 metal pins along with the plastic motor-mount.


Image 4. Backside with 2 screws and the end-cap.

Once opened, we can see that the handle is only used for the 2 AAA batteries. The control switch is a simple double-pole double-throw switch made cheaply on a small circuit board and held in place by the case. The switch cannot be easily salvaged.


Image 5. An opened IGO.

Geartrain

The geartrain in the IGO Mini Screwdriver is real nice. It has 5 stages for a reduction of 70.5. The hex connector also has a magnet in the end. The metal screwdriver bits slip into the hex connector and are held in place by the magnet.


Image 6. Details of the geartrain.

Speed:

Using the 2 AAA batteries that come with the screwdriver, the output rotates at 160 RPM. Applying 5 volts to the motor, it turns at 280 RPM. Running it from 5 volts for over a minute did not heat up the motor. The motor can be easily driven using your favorite technique, such as an H-bridge, DPDT relay, or other DC-motor driving circuit. Speed can be controlled using typical PWM control. Here are a few DC-motor control references I see in Google:

For use in a small robot, I cut the plastic case down to the minimum needed to keep the motor and geartrain together. I used a cutoff wheel on a Dremel tool to do the cutting. My plan is, with the notched case, to be able to place two of these back-to-back with the notches interlocking while keeping the axels in line with each other. This should be easy to get the wheel-to-wheel width to less than 5 inches. For mini sumo robots as used in the Seattle Robotics Society Robothon events, the maximum width is 10cm (about 4 inches). With some creative cutting of the case, maybe cutting the hex connector shorter, and possibly offsetting of the wheels, these IGO motors and geartrains should be useful for the mini sumo robots.


Image 7. Hacked case for robot use.

Mounting:

For mounting this hacked screwdriver to a robot there are many options. I'll discuss a few that occur to me before I actually try to mount them.

Conclusion:

For $5.99 (sale price of $2.99) I got a bunch of useful items for my robotics work. Here's a comparison based on other products at Fry's:

I hope this quick article was useful to you. Please let me know if you build a robot using these techniques. I suspect they will make lots of great robots.

Tom Dickens
no-spam-address - - - tom-at-tomdickens-dot-com