Amazon.com: Customer Reviews: SainSmart 16-Channel Relay Module
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on January 24, 2013
I have had a hard time getting accurate (correct) specifications from SainSmart, so I wired it up and took measurements.

So here are some specifications that we can all use:

Overview:
1. The 12VDC input requires > 500mA.
2. The drive to each control input pin must "sink" 3mA when low (low = relay ON).

By the way, this is a great product - awesome bang for the buck!
Note the price has gone up (was $23.69) ... less "awesome" but still "Good" bang for the buck.

***** Input Power (12 VDC input)*****
- About 8 mA is required with all relays off.
- Each relay requires about 30 mA when on.
- So max supply current is 8 mA + (16 x 30 mA) = 488 mA (actual measured was 500 mA)
- Because one may use the board's +5 VDC output (2 pins) to power an Arduino/PIC circuit, use a 12V power supply that can provide MORE than 500mA (depending on your circuit's requirements).
- Note that the switching regulator on the Relay Board should somewhat efficiently (say 70%?) convert the board's 5V power usage to 12 V power input requirements. For example: 200mA at +5VDC (1 Watt) does NOT mean the +12V supply needs to supply an additional 200 mA also. This is because 1 W of power from the +12V supply only requires about 83 mA ( 12 V x 83 mA = 1 W ); however at say 70% efficiency of the 5 V regulator, this goes up to about 120 mA (83 mA / 0.7) but NOT the full 200 mA.

NOTE: The best way to discover what 12 V supply is needed (its max current rating) is to ACTUALLY MEASURE the 12 V input current while using a "test supply" that can more than handle worst case (with all relays ON) then buy the supply that meets your needs. Always use a modern "switching" supply (wall wart) because they are smaller, way more efficient, generate little heat, and normally use much less "vampire power".

- The baord's LM2576 (+5V) voltage regulator is rated at 3 Amps; however, one should not push it this hard. The circuits powered by the 5 V supply on the Relay Board appear to only be the LED side of the opto-isolators. Driving an input control line low turns on an opto-isolator LED ... turning on its relay. Each opto-isolator LED seems to require about 3 mA (for a total of 3 mA x 16 = 48 mA). This should leave you with at least many hundreds of mA available to power your circuits off of the relay board's 5V output pins (two of them on the connector).

***** Input control pins *****
- Grounding an input control pin (logic low) turns on the associated relay.
- The circuit driving the input control pin must be able to "sink" (drive logic low) about 3 mA of current (easy for most PIC/Arduino output pins).
*** CAUTION *** When a pin is NOT driven low, it "floats" to nearly the +5 V that drives the opto-isolators. This means that the driving circuit (Arduino/PIC) must either be also powered by +5V, or if powered by the now common 3.3V (or less!), its output pins must be "5 Volt Tolerant" (see your micro-controller pin specs). Another option is use of a "5V tolerant serial port expander" chip like an MCP23018 (I2C interface) or MCP23S18 (SPI interface) ... where just a few micro-controller pins give you 16 I/O pins. These can be powered by 3.3 V or 5 V. They are a bit complex, but a simple "software bit banged" I2C or SPI interface can be used to control them. Finally, one could use little signal transistors (2N3904) for this isolation from the 5 V (MCU pin -to- a say 2.7K resistor -to- transistor base, emitter to ground, collector to relay board input control pin).

Darrell Thayer
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on November 9, 2012
Ok, I admit it, it took me way too long to figure out how to hook this thing up. In case anyone else is looking at this and wondering how it works, here's how it gets hooked up:
1) The header pins on the bottom of the main picture get wired directly to the Arduino board. Connect one of the 5v pins to a 5v header on your Arduino and connect one of the Gnd pins to a ground header on the Arduino. Each one of the relays has a corrosponding header down there, too, which get connected to a digital output on your Arduino. You can run each wire individually or run over a ribbon cable to a project board and break it out from there. Either way, getting the header pins hooked up allows the logic to fire, and makes the lights work so you can at least diagnose/debug your program.

2) Next, the relay board needs a 12v dc input wired up to the blue terminals on the bottom. These are wired to the relays, which make the relays actually fire. The voltage magnetically pulls a piece of metal away from one pole to the other. This action makes a noticeable clicking noise, which is a little annoying, but also lets you know it's working.

3) Each relay has 3 terminals located along the sides. One side is normally opened, the other is normally closed. Use this to either make or break the circuit that you have wired up for your lights, motors, or whatever else is involved in your project that draws more than 5v or needs to be kept isolated from the Arduino board.

So yeah, keep in mind that you'll need a 12v power source to actually make the relays fire. All in all, it's a very well put together board, and would make a great control hub for something like say... a model train set or robot.
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on January 7, 2012
Received this relay controller a few days ago and it is absolutely amazing. The controller requires 12V of power and I used an older wall wart from a dysfunctional wireless router. It did take me a while to figure out how to get everything properly wired but after a little tinkering.

A little help for anyone else that purchases this relay controller:

1. It needs 16 digital pins to independently control all the 16 relays. The Arduino Uno has roughly 10 usable pins so an Arduino Uno is not ideal if you want to control all the pins independently. An Arduino mega would be the ideal choice for getting everything running perfectly.

2. The female header on the controller has two ground pins and two 5V pins. Once the relay controller is connected to a 12V power source the controller will provide 5V of power on both of those 2 5V pins. Which means you wont need another external power source for the Arduino. One thing to note is that if you connect the USB cable after the relay is giving the Arduino 5V of power the USB will not connect. Disconnect the relay 5V pin from the 5V pin on the Arduino then connect it back to USB to solve the issue.

3. The relays are loud. If you're going to use this to control something that will regularly turned on or off you'll probably want to put it into some type of enclosure to keep it quiet.

Overall this is a great product, I recommend it to anyone looking to control some Christmas lights or setting up a home automation system.
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on January 5, 2012
Just received the SainSmart 16-Channel 12V Relay Module for Arduino and am surprised there was no pin-out or schematic included in the shipment, not even a link I can download it from. Disappointing because now I am waiting for an email response from SainSmart (just sent 30 minutes ago) hoping they supply me with documentation. Every developer device I have ever purchased comes with a Pin-out and a schematic, why would they not include this?? I have tinkered with it a little and found you have to supply +12VDC to the right pin on the blue terminal (labeled 12V) and the negative of that same 12VDC supply to the left pin (labeled GND). This energizes the LM2576 voltage regulator and associated circuitry and energizes the 5V and GND pins on the 20 pin header (potential across GND and 5V pins will give you 5VDC). If I connect a wire from the GND on the 20 pin header to any pin 1-16, it energizes the associated relay. EXAMPLE: connect GND of 20 pin header to pin 1 will energize relay K1. What is a little unclear is why the board supplies 5VDC. I was under the impression the relay is looking for 5VDC and that would come from one of the Arduino Uno outputs? Will update when I find out more.
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on May 26, 2014
I bought this to use with the Raspberry Pi. It comes with absolutely no documentation at all, either in the package or on the manufacturer's Web site, and therefore it's taken me quite a while of puzzling through Google research to figure out how to use it. There are some answered questions in the Amazon product description that have been very helpful as well.

My configuration is that I use a 12v power supply to power the board (which powers the relay coils), and from that the board derives 5 volts to run its electronics. I am using this 5v to power the Raspberry Pi by connecting the 5v pin from the relay board's header to the 5v pin of the GPIO header on the Pi. I'm not using the standard Pi power connector. For each relay that I want to control, I'm using a 1K resistor between a GPIO pin on the Pi and one of the control pins on the relay board. When I turn the GPIO pin off, the board energizes the relay; turning the GPIO pin on releases the relay. (That seems a little backwards to me, but it works fine. I can control my load either way, because the relays have both NO and NC contacts.) I can control the GPIO, and thus the relays, from Python. I'm trying it control it from Java directly, but that's been hard for me to get working. The Python libraries have been easy for me to figure out. I'm hoping that eventually I'll figure out the Java as well.

The product design and build quality both seem to be first rate. The price is excellent -- you could scarcely buy the 16 bare relays for the cost of this board. But I have to knock off one star because of the complete lack of documentation.
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on March 23, 2016
I just ordered six more of these boards via Amazon Prime. They are an incredible bargain, and available for even less on eBay if you don't mind waiting a few weeks for shipping from China.
Because of previous reviews, I examined these carefully and tested every one right away. All of mine had clean, excellent build quality, and every one worked perfect out of the starting gate. Many electronic products that come out of China are of poor quality, such as some of the Arduino clones, but this Sainsmart product is very high quality.
There is a lengthy review of this module by Darrell Thayer, which provides a lot of measurements on current etc. I tested all of these values with my Fluke 177 and all of Darryll's numbers are spot on.
I'm using these relay modules, along with an Arduino microcontroller and "Centipede" shift register board, to control turnout solenoids, accessories, and other devices on my model railroad.
Incidentally, it doesn't say if these are rated for continuous duty or not. I powered all 16 of the relays and left them energized for a few hours, and while the relay housings were a bit warm to the touch, there was no sign that they were burning up. None of the chips were warm to the touch.
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on April 9, 2015
Works as advertised. There is no manual or instructions or much to be found on-line to explain how to make this work. Once you understand how to make it work, it works as you would expect. It comes in at under $3.00 per relay, so the value is there. Appears to be well built, good solid PC board, good support electronics, hearty relay contacts and a design that provides a high level of isolation on the very easy to drive input.

I ended up writing a document that explains how and why this thing works. Check out some forums to find my pdf. (hint: search rufus and sainsmart)
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on December 6, 2014
Inexpensive, but did not feel cheap. I misread the wiring diagram on them at first, but that was my fault for not really understanding the relay diagram. The pin in the middle toggles from one side to the other based on power. If the relay is energized it will connect the circuit opposite what it on the board. Once I cured my ignorance on this topic through the magic of the internet, this board did everything I needed and worked perfectly. I was able to drive it with a Raspberry Pi using two ULN2003 chips and a 12VDC power supply (to power the relay controller) with a 5VDC regulator to feed voltage for the individual relays from the ICs to the relay controller. Everything is labeled clearly, but the header pins on the board are pins, not sockets, so keep that in mind when deciding how you're going to hook it up. There are plenty of options here on Amazon which work perfectly.
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on April 8, 2015
Good board that works well. Just note if you're using with a RaspberryPi, you'll want to get:
http://www.amazon.com/gp/product/B00BWYS9BA/ref=cm_cr_ryp_prd_ttl_sol_18
http://www.amazon.com/gp/product/B00BWC4BHS/ref=cm_cr_ryp_prd_ttl_sol_16
http://www.amazon.com/gp/product/B0092CRK5A/ref=cm_cr_ryp_prd_ttl_sol_20

so you can interface the the board with the GPIO's (the rasp pi's GPIO's are too weak to run the board directly). Once you set it up though, it's a nice board. The only issue I had was running my Christmas lights off of it, and that was only because I was using PWM and had it modulated to provide a fade.. I had too many lights off of the one relay (using 6 channels so a total of 6 relays in use) and would get a night or two nights use out of the one relay before it would stick in the on or off position. The other 5 relays held in fine even though they were being cycled at a rate of like 70+ cycles a second for a couple hours a night.
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on January 8, 2016
Don't hesitate - this info is only if you have trouble, and for the manufacturer:
I fixed the 1 bad channel! It wasn't an optoisolator chip (replaced), it was a single bad resistor in the SMT cluster chip, so I just cut the trace and soldered one to +5 and opto input on the bottom of the board. No problem. SMT can be so fickle. Ha!
Thanks for a great product! This is my 2nd board, FYI.
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