How to Turn on a Triac With a Basic Stamp
A triac is a semiconductor device that allows a signal measured in milliamps to control the flow of large AC – in the range of hundreds of volts and double-digit amperes. The name comes from “Triode for Alternating Current” and was formerly called a thyristor. Triacs replace mechanical relays, which were formally used for controlling large currents. Stamps are programmable microprocessors that can output control signals under software control. Working together, stamps and triacs can be used to control anything from large earthmoving equipment to small chemical factories.
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Instructions
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Develop a controlling algorithm and write it in PBASIC -- the language used to program the stamp microprocessor. PBASIC is just the parallax version of the BASIC programming language. It contains all of the BASIC control structures plus commands to designate chip pins as input and output channels and commands to put signals on the output channels.
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Connect the stamp to your PC via a USB connection. Bring up the PBASIC programming environment and type in your control program. Thoroughly test and debug your program and then download it onto the chip.
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Adjust the stamp outputs to match the triac input requirements. The outputs of a stamp are always a signal that varies between five volts and zero volts. The purpose of the DC-16 is to take this input signal and translate it to any value that you program into the DC-16.
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Tips & Warnings
One factor that definitely contributes to the popularity of stamps is the simplicity of programming them. The instructions to select pin 3 for an input pin and pin 5 for an output pin are “in 3” and “out 5,” respectively. The instructions to output five volts and zero volts on pin 5 are “high 5” and “low 5,” respectively. The code to output a signal that consists of 10 pulses lasting 1,500 milliseconds with 300 milliseconds between pulses is “for i = 1 to 10 high 5; pause 1500; low 5; pause 300 end for.” PBASIC has all the control of BASIC plus a few simple instructions for input and output signals.
When developing control systems for high voltage -- and probably expensive -- equipment, it is a good idea to go through an extra test step. Once the stamp is programmed, make a network of triacs that are not actually connected to anything. Run the program and test that each triac is operating properly with a multimeter. This extra test step takes up a little time but can save a lot of money, destruction and embarrassment that can result from putting an untested program online.
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