Efficient way of driving latching relays

If you need to keep relay turned on or off for a long time, then standard relays may not be best solution. First of all in order to keep relay switched, power must be applied. If you are using mechanical relay, then coil must be constantly energized. This way relay draws power and for battery operated equipment this is not acceptable. SSR relays might be a better solution, but signal still need to be applied in order to keep it turned on. In such cases there are latching relays used. These relays keep their state after switched and power is removed. They are common where relay need to be on or off for long time. Controlling such relays is a bit trickier than regular ones. First of all relay can… Continue reading

How to drive bipolar stepper motor with basic stamp

Bipolar stepper motors are common in printers. They are different from unipolar steppers. Bipolar steppers usually have four wires (while unipolar 5). Bipolar stepper motors can be driven by using H-bridge circuit like SN754410 from Texas Instruments. One SN754410 IC can drive single bipolar stepper motor. In this example you may see two of them, so each motor is controlled via separate H-bridge IC. Whole circuit is built around Basic Stamp BX-24 which can be programmed by using Basic language. Sample source code is available for testing. Continue reading