Wrobot / Emartee / Ywrobot relay board...

THAT was entertaining... not.

I saw an image of what looked like a nice relay board. On it was "Ywrobot", so I went looking for a supplier.

There IS something on the planet which Google has hardly heard of... "Ywrobot".

In the course of my quest, I came across http://www.emartee.com/ ... who seem to be distributors for a bunch of fun Arduino stuff, includng stuff very like the relay I was interested in... under then name "wrobot". Hadn't heard of Emartee or WRobot (or YwRobot) before. Anyone have experiences, good? bad? Emartee's "about us" says: "We are based in Shenzhen, China where large number of exciting and innovative products are manufactured. We supply Arduino Series?Arduino Bricks ?Arduino Shields?Arduino Gadgets?Arduino ICs? ARMs?LEDs?LCDs?Wireless Modules ?Sensors?Motors?Cables?etc ." I for one have had very good experiences dealing with such operations, but do not know Emartee, specifically (yet). And if you visit News, Electronic & Electronics Components Depot United States, you will find distributors in many countries... no international shipping hassles... for you. (I have things shipped from China without hassle, but you may not want to take the chance.)

Search eBay for Wrobot, and numerous things turn up, many from emartee2009 on eBay, a seller since June 2009, 2000 transactions, 99.7% positive feedback.

Discovered that wrobots.com is probably NOT the source. Their site has goodies, too, over the line "Most of the motors and parts found on this site were pulled from recycling operations. Support recycling!"

http://www.wrobot.com/ (no s) doesn't seem to go anywhere.

My guess at this point? Wrobot is a brand name used by Emartee. The "Ywrobot" on the board, that sent me off on this web-quest was a typo, or a deprecated false start.

As I said... any fans or furious people out there, re Emartee or Wrobot?

Further to the above...

The "About Us" at....


... (where you can buy lots of neat stuff, shipped, I believe, from a distribution point in the US)...

... says....

"YourDuino is the creation of Terry King and Jun Peng. This is a partnership and collaboration between two friends: An old Engineer from the USA, now living in Saudi Arabia, and a young man from China who is contributing his energy and his knowledge of the Chinese markets to bring you interesting, high-quality products at low cost."

Terry often posts in the Arduino.cc forums, and no, I don't know him, he didn't put me up to this!

(arduino-direct.com is the "shop" you can go to from http://yourduino.com/ which has lots of good tutorial material)

As I said... any fans or furious people out there, re Emartee or Wrobot?

Just one comment. Looks a bit boot-leggy to me...


I can explain the YwRobot mystery somewhat. They are a Chinese company that sells mostly to the chinese market. They have some nicely-done products.

I lived in China for 2 years and recently started the online YourDuino.com shop selling low-cost Arduino related things from the huge Shenzhen electronics market (900 shops!!). There are also hundreds of large and small electronics manufacturers in that area (and huge ones like Foxconn)..

My Chinese friend Peng had difficulty really tracking YwRobot down but finally made contact with them and we are a distributor for their products. I am just evaluating and testing more of them. You can see the Ywrobot Taobao shop here: http://ywrobot.taobao.com/

The relays are quite nice and high quality. You can see many of them on my site here: http://goo.gl/8ZEQ8 (short url).. We also have some optically isolated relay boards. They make the relay boards with 1,2,4 and 8 relays. Nice!

BTW these relay have active-low inputs, which could possibly be a startup problem. See my code example here: http://arduino-info.wikispaces.com/ArduinoPower

The electronics scene in China is fascinating and convoluted and difficult to penetrate, even for my knowledgeable Chinese partner. It is easy to get products on Ebay but difficult to get past those middlemen who are protecting their sources. And I am finally getting some technical information about more products as we become more trusted by the Chinese manufacturers.

I'm not making any money on this yet, but my partner is making a living and we believe in the future of Arduino and smart DIY.

I'd appreciate any suggestions for other product people are looking for...

DISCLAIMER: Mentioned stuff from my own shop...

Regards, Terry King
...On the Mediterranean in Italy

okay, i just bought one of the relay modules on amazon for 9$ i am wondering what code do i write to make this work? Any help? Thanks in advanced.

Hi, Use the code here to start:

Lots of other relay/power how-to there also...

Hey Terry,
I'm so glad I found this thread. Your website was everything I was looking for. I'm somewhat new to Arduino and brand new to Arduino relay breakout boards. Since the documentation is scarce on the Relay Module from SainSmart, your tutorial was key in understanding how to move forward with this piece so thank you so much!

There's a Sparkfun tutorial Controllable Power Outlet - SparkFun Electronics that picks up from where you left off as far as creating a safe connection to a wall outlet. I don't have all of the parts with me tonight but I now know what to get.

So thanks again and I'm going to be combing through your website for sure!


Hi Eric,

Thanks for that pointer; I've seen a couple of things like this but that is the best description I've seen: Controllable Power Outlet - SparkFun Electronics

Most outlets (AKA "Duplex Receptacles") can be separated into two circuits. Usually there is a small metal link that can be broken off. Then a small 2-relay board like this could be used to control two separate things plugged into the two receptacles: http://goo.gl/jJRYM

Another good possibility is to use a small optically-isolated "Solid State Relay" that can be easily driven by Arduino. Example: http://goo.gl/jbNwl

I really prefer the optically-isolated relays: Your Arduino is doing nothing but turning on an LED inside the relay driver.

More relays here: http://goo.gl/8ZEQ8

DISCLAIMER: Mentioned stuff from my own shop... which is what I know about!

I have this Ywrobot Relay board. I've built a remotely controlled power outlet with it. It works perfectly well when nothing is plugged into the outlets. However, when I plug a lamp or anything into the outlet and switch the relay, Arduino frequently locks up. I guess this board doesn't do a great job of de-coupling the power supply. Any idea how I could improve it? Adding a capacitor or an inductor to the board perhaps?

Here is the circuit of this relay board:

And here is a link with some additional pictures: http://www.ebay.com/itm/Two-2-Channel-5V-Relay-Module-Expansion-Board-For-Arduino-ARM-PIC-AVR-MCU-DSP-/221009967173?pt=LH_DefaultDomain_0&hash=item3375387845.

There are two things to consider here:

  • Isolation of Arduino from the relays themselves and their switching transistors and power supply
  • Isolation of your power wiring from arduino and it's wiring

Let's look at the choices of relay boards. There are two widely available types of relay boards, and lately they cost about the same.

  • Boards with a common Ground and +5V supply between the Arduino and the board.(The one you show above)
  • Boards with optical isolation that can be run with no direct electrical connection between Arduino and the relays and their power supply.(Which I will show below)

"Optically Isolated" means an "Opto-isolator" chip is used. See: http://en.wikipedia.org/wiki/Optoisolator So only a beam of Infrared light (The little blue arrows in the diagram below) connects the Arduino circuitry to the relay and switching parts. Here's what an opto-isolated board looks like, followed by it's circuit diagram, and a photo of the opto-isolator chip:

More details of this opto-isolator are here: http://arduino-info.wikispaces.com/Popular-ICs (Scroll down).

Let's look at how to connect the relay board so it is really isolated. Notice that board has a jumper between "Vcc" and "JD-Vcc". Remove it. For complete optical isolation, connect "Vcc" to Arduino +5 volts but do NOT connect Arduino Ground. Connect your Arduino Digital Output pins to "IN0", "IN1" etc. Connect a separate +5 supply to "JD-Vcc" and board Gnd. This will supply power to the transistor drivers and relay coils. Look at the diagram above. Only the part to the left of the small blue arrows is connected to Arduino.

Wiring and cabling issues:
You're not home free yet, because if you are switching large loads, especially inductive loads like motors, etc. you may still have "EMI" (ElectroMagnetic Interference) problems.http://en.wikipedia.org/wiki/Electromagnetic_interference

People who have designed computer-driven automated machinery know that they have to be careful about the physical routing, shielding, and isolation of low-level computer/Microcomputer electronics and high-power motors and loads. Here are a few guidelines:

  • Physically separate the low-power Computer/Electronics part from the large power-handling part
  • Pay special attention to Grounding: Create a single common ground point in the power section. Connect the Computer/Electronics ground to it at only that one point.
  • If possible locate all the power switching devices/relay in the power section, as close to the load as reasonable
  • Run connections to the relays etc. from the Computer section to the Power section in shielded twisted pair (or at least twisted pair) wiring.
  • Minimize the Electromagnetic Interference put out by the loads by putting suppression devices like MOVs (Metal Oxide Varistors) across them.
  • Test the switching by attaching a simple light bulb load. When everything works, try the real heavy load. Then you will know if you have EMI problems.

OK, that's a big deal. What can we do that's simple and helps? I'd suggest this:

  • Locate the relay board close to the load, (like in the outlet example)
  • Locate a separate 5V supply near the relay boards, plugged into the Load power, not near the Arduino power supply or a computer supplying USB power to Arduino.
  • Run CAT5 cable back to Arduino, one pair for +5V and Arduino ground (NOT connected on the relay end if you have opto-isolated relays), One pair for each signal, with one wire connected to ground at Arduino, the far end unconnected
  • Run the Arduino from a separate 9V supply, not USB connected to a computer

Maybe we can start another thread just about relays and power switching in general. Opinions??

More about power/relays here: http://arduino-info.wikispaces.com/ArduinoPower Lots of relays here: http://goo.gl/8ZEQ8

Lots of people are successfully controlling lighting, home devices, complex aquariums, Aquaponic Systems , etc etc. with relays like this.

DISCLAIMER: Mentioned stuff from my own shop...!

Thank you for your detailed response. It looks like I will have to replace my relay board with one with optical isolation. I hoped I could avoid that because it is already built into a custom box. Ah, well...

Hi, Before you do that (or while you are waiting..) try some of the other things, like separating the wiring, using shielded wire to the relay coils etc.

This is just a follow-up. I could not try those other solutions because I only have one power supply available and everything was already fully wired up. However, I got a new relay board, the one that is on your picture, and it works perfectly well. So it's all good now!

If I may add 1 cent.. I just got one of those boards, model is 530677. It's transistor based board with GND connected to both relay and logic.

What bothers me is: the VCC going from NPN transistor's collectors run past relay mains less than 1mm apart for all 8 relays! This will be a real blast when using 250VAC and I think I will go implement my own solution.

Just wanted to let you know.

A secondary relay can be added, triggered by the first, so that the high voltage doesn't have to pass through the board.