Motors and Sensors

Getting a Handy Board is only the have to connect it to some motors and sensors in order to bring your LEGO creations to life.


Although non-LEGO motors can be used, I decided to stick with LEGO motors for my work. I felt that it would simply be easier to build LEGO motors into my creations. There are presently three different LEGO Technic Motors, all of which use a 9v power supply and use standard LEGO style electical connectors.


The Handy Board includes 9 digital and 7 analog input, all of which use identical connectors. The connector is a 4 pin .100 spaced header with 1 pin missing. If we number the pins from top to bottom we get:

Passive sensors, such as switches, merely require sense and ground connections. Remember that on the Handy Board, each sense line is pulled up to Vcc by a 47K resistor. This means that an open connection will read as 5V, a short circuit will read as 0V, while a 47K resistance between sense and ground will read as 2.5v.

Active sensors are read the same way, but may use Vcc to supply power.

Digital inputs are wired identically, but can only differentiate bewteen two readings: on and off. The threshold is roughly 2.5 volts, but should not be assumed to be exact. In general, the digital inputs are best suited for things like switches.

Several different LEGO sensors are available. The passive sensors (touch and temperature) can be directly connected to the Handy Board - just connect the outputs of the sensor to the sense and ground pins of a 4 pin header and plug it into the Handy Board.

In theory, it should be possible to connect the active LEGO sensors to the Handy Board, but I do not know yet the specifications of the LEGO active sensor connections.


Making Connectors

The Handy Board uses a 3 pin .100 spaced header (with the center pin unconnected) as a motor connector. LEGO motors use a special 2x2 plate with electrical contacts. There are basically two different ways to get the Handy Board connected to a motor.

The first way is to cut a normal LEGO cable (such as set #5111 from S@H) in half, and solder .100 spaced headers onto the ends of the wires. This is the easiest procedure but can be a bit expensive in the long run since you only get 2 connectors out of a $4.50 cable.

Another option is to make your own cables - the only tricky part is getting a 2x2 lego plate on the end. S@H sells a set (#5037) which contains 4 2x8, 3 2x4, and 2 1x2 electrical plates. By cutting the 2x8 and 2x4 plates into 2x2 sections you can get 22 connectors - not bad for $6.75. Once the plates are cut up, you just solder appropriate wire (I use 20 gauge stranded) to the edges of the underside of the plate's metal connectors. It takes a bit of skill since you don't want the wire or the solder to interfere with a piece connecting to the plate, and you have to be careful not to damage the plate with excessive heat from the soldering iron.


Build a Touch Sensor

Do you think $18 is a bit expensive for a simple switch? If so, you can build your own touch sensors.

Still under construction. No pun intended.

Build a Light Sensor

Still under construction. No pun intended.

Note: S@H is short for Shop at Home, LEGO's mail order service for the U.S. They carry sets not available in the general retail stores, as well as spare parts kits. They can be reached at 1-800-453-4652.

 [Dave's Lego Site]