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so I'm trying to control some solenoids to control water flow and I'm using the Sainsmart 5v 4-channel relay board to step up the voltages to the correct values for the solenoids. for the purposes of this discussion lets only look at one solenoid to control, and follow through the wiring required. My issue is the conditions of the TS-7500 being turned off, during power-up, and the default states of the gpio. When the unit is powering up the gpio pins are all high. As such this would open the solenoids if I used these pins directly on the relay boards. This is not acceptable. conversely if I open the solenoid on signal going low, the solenoid will open whenever the ts-7500 looses power. also not acceptable. The sainsmart 5v 4-channel relay has a an opto-isolator relay to hook up to the gpio pins to control sending the board power 5v to control the big relays. What I want to do is use two of the gpio pins for the control one pin (A) on the +(annode?) side, and the other pin (C) on the -(cathode?) side. In this way, while the pins are set the same way, the opto-isolator won't allow passage from collector to the emmiter. After the ts-7500 is booted up, I can then set Pin A to 3.3v(on), and pin C to 0v(off) and allow flow of from the collector to the emitter. Here are my questions: Can the TS-7500 GPIO pins source enough voltage/current to control the opto-isolator? The ts-752, the interface board for the TS-7500 has "output Pins" what are the voltages/current limit of those pins vs the general gpio pins? The ts-750 also has Relays built into it, I'm assuming if 1) or 2) can't handle the load to drive the opto-isolator I can use these to do (at least 3) of the opto-isolators? Any help/insight into this would be appreciated. - Jleslie48
http://www.sainsmart.com/4-channel-5v-relay-module-for-pic-arm-avr-dsp-arduino-msp430-ttl-logic.html
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