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HowTo: Velleman K8055 & SSRs
( dave haberle)
Step 3 : Build the SSR-2009D boards
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| | This SSR-2009D design is a derivative of Sean Bowf's miniature 4-channel SSR by adding diagnostic LEDs and instead of providing +5v power to the optocouplers and switching the ground, it is reversed so that ground is common and +5v is switched. This allows connecting two SSRs directly to either the 8 outputs from a computer’s standard parallel port or a Velleman K8055 USB experimenter board (see easy Velleman modification notes above). However, in its raw state, it also makes this SSR incompatible with an Olsen 595, Grinch or other board that supplies +5vdc everywhere and switches ground. At the end of this how-to, I will offer additional information that can make the K8055 compatible with the 595 and Grinch SSRs. Also changed are two A/C power leads for each of the four outputs (stranded speaker wire is about the same gauge as the wire in a typical light string and works fine). The board isn’t as compact as Sean’s, but it’s still quite small – about the size of a credit card.
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