I'm looking to use several (12-18) solid state relays to control a set of water valves (24V AC solenoids, 20ma holding current, 40ma inrush current), and I'm having trouble finding suitable parts, probably because I don't understand the datasheets I'm reading very well.
Most of the low-current (<=150mA), inexpensive (~$1) SSRs that I've found have maximum "input forward voltage" ratings in the 1.0v-1.5v range (see here for a typical example). Does this simply mean that I need a 38 ohm resistor between my MCU (3.3v) and the SSR?
What do the other ratings mean, such as these:
- Repetitive peak OFF-state current (output)
- ON-state voltage (output)
- Holding current (output)
- Minimum trigger current (transfer)
I assume that ON-state voltage is the minimum voltage required over the output of the SSR for it to turn on, so at 24v, I'm well above the minimum, correct?
Minimum trigger current and holding current are the amounts of current across the output required to turn and keep the SSR on? Wouldn't the current drop to zero at the zero voltage crossing? I'm not sure what these ratings mean.