SainSmart 4-Channel 5V Relay Module for Arduino DSP AVR PIC ARM

Here is a short video of the relay module hooked up and working to give you an idea of what you get. I am using an old basic stamp microcontroller, but anything with 10-20mA output currents will be to cycle through each input line to switch the relays. There is not a lot of information available online about "Ywrobot"(the company whose name is on the board) or "SainSmart"(the advertised name) so I wanted to clear up any confusion about this product and what you are getting.

I don't really know why this is listed as a toy as it is a piece of electronics hardware that can theoretically switch up to 4 x 10 amps @ 250 volts.

The board is well made. It is properly designed insofar as the relays default powered off with an open connection and stay off with a 0V connection and only pick up with a positive control voltage. A different board we tried energized the relays if the control connection was open, which is difficult to work with. (Like if you're controlling it from an Arduino, the digital pins are open until you configure them for output.)

Under a loupe it's clear that the surface mount components were hand-soldered and a few of the solder joints look a little less than perfect, but we've bought several boards and they've all worked fine.

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I just opened up this product and couldn't wait to play. It does work as it should but there are a few kinks that a simple set of documentation would have avoided right away.

I wired my output load to the leftmost (looking at the card with the row of output terminals pointed upward) two terminals of the three terminal block for each relay.

On the input side of the card, applying a logic level high (+5) to the input pin for each of the relays cause the relay to close and energize the output load circuit. However, the indicator LED on the card actually go off. Driving the input pin to ground for each relay opens the respective relay and de-energizes the output load circuit for that relay and the indicator LED on the card associated with the relay being controlled goes bright.

The behavior of the indicator LED as related to the state of the relay is a little counter intuitive but once the multimeter set me on the right track, I had a veritable disco on the kitchen table with a couple of test lamps switching at upwards of 50Hz. Nice toy for the money.

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Great with Raspberry Pi!

This thing is super responsive. It's worth every penny and then some. It's been a great joy working with it. And the built-in LEDs (one per input/relay) help test the inputs.

How do you use this thing? Connect VCC to +5v. Connect GND to ground. Connect any of IN1/IN2/IN3/IN4 to any of the GPIO/control pins. If the input LEDs don't light up, be really sure that you have VCC and GND connected correctly. Use a multimeter to verify this if you have one handy (and if not, buy one!). If you want to just test to see if the input works, connect any of the input pins to GND and it should cause the relay to click on and the LED for that input/relay to light up. If you don't get that, you did the VCC and/or GND wrong.

If you're using this with a Raspberry Pi, all of these pins (GPIO, +5v, and ground) are on the P1 header. Assuming that the pin up against the P1 marker is pin #1 and the pin across from it is pin #2: +5v is pin #2, ground is pin #6, and then pick any of the GPIO pins. You'll have to look up the GPIO pins on a Raspberry Pi site since Amazon will strip out any links I put here. For example, GPIO4 is pin #7.

By the way, this product is categorized as a toy but it obviously doesn't belong in this category. I would like to think that the person at Amazon that will be reviewing my review of this product will notice and do something about it. I shouldn't hold my breath.

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Short version: Mine didn't work.

What's odd is that apparently while QC does test these, they don't test enough to ensure they actually work. On mine you could see a makeshift repair on the vcc line where the mask was scrapped off the trace and a solder bridge was made to the VCC pin and trace. However the through-hole plating was bad on the input pins so the circuit did not work as designed. Mine drew 2 amps on 5v, which was what alerted me that something was definitely wrong. I tried a repair, but ended up lifting a trace in the process so this item got tossed into the junk box to maybe later desolder the relays. Perhaps I was just unlucky with my purchase, but this item did not work as advertised.