HiLetgo Relay Shield 5V 4 Channel Arduino UNO R3 Relay Shield Arduino Shield

Received this, a couple of pins were bent, but nothing that a quick straightening didn't fix. As other reviews have said, there are 3 pins that stick down and will touch the shield of the USB connector on an Arduino. Place some electrical tape on it. This is not a worry for me as I am using this for prototyping and testing and not the permanent installation.

I should've gone through some of the reviews, but I didn't. I simply looked at the description, saw the price, saw the Prime delivery, and bought it. After all, who would think that something as simple as a relay board for an Arduino could turn into THIS level of trash? As others have rightly pointed out, the pins from the screw terminals come into direct contact with the metal USB connector on the Arduino. This can short out and kill not only your Arduino, but also the computer that you're using for programming it. That's in addition to bent pins, horrible quality of components using the absolute cheapest possible junk that they could scrape together, and the sheer sloppiness of the way in which the board was put together. Even after you take into consideration the fact that it's cheap Chinese-made garbage, this thing still manages to be astoundingly bad. China is famous for ripping off intellectual property and copying other people's work. But the absurd thing is that with this particular product, they didn't have to steal or copy or reverse-engineer anything because all of the original schematics from Arduino's relay board are available for anyone to see. And yet, despite that, they still managed to create this monstrosity which has the potential to not only destroy your equipment, but could very well create an electrical fire and burn down your entire home or business. It's actually quite infuriating that Amazon hasn't pulled these things off their site, especially when you consider that people have been complaining about the design problems since 2019. Avoid this thing like the plague. By doing so, you'll save yourself a lot of grief, and quite possibly save yourself from having to deal with the aftermath of your house or business burning to the ground. Go and buy the original relay shield from Arduino. Yes, it's a little more expensive, but the difference in quality is night and day.

The PCB appears to be of good quality and well assembled. However the pins were bent in 14 different directions. Since they were embedded in sponge, it is hard to imaging it happened in shipping, but rather at the supplier. As another remarked above, the connecting pins are remakably flimsy. The pins were so bent that it took me 15 frustrating minutes to align everything and mount it on the Arduino board. The headers for the boards the mount on top of this shield were also askew. Whether this occurred inshipping or assembly is difficult to judge. Although the blurb suggests that the unit will work with a 3.3V unit (I quote "4. High Drive (5V or 3.3V) normally open contact closure"), there are no specifications or schematics to check whether to transistors, together with the resistors are in fact compatible with a 3.3V input.

This shield has 4 active high relays. This means they turn on when you send a high signal from the micro-controller. I used an Arduino clone to test and it works great. Feel free to use my sample code in the picture.

Be aware of a potential short circuit. The thru-hole pins that solder the components on the top of the board are not trimmed flush with the bottom of the board. As a result, the connector block for relay #1 will definitely short itself to the USB-B connector on the Arduino Uno board below. In fact, those protruding pins may actually prevent the relay shield above from fully engaging the Arduino below. In any case you will need to trim those three pins before using this relay board. A small side cutter tool that trims flush with the surface would be very handy. I didn't have one of those, so I clipped off the excess length as best I could using ordinary wire cutters and finished the trim by filing down the pins with a jeweler's file. That took quite a while because those pins are plated steel, not soft copper. When I finished the trimming process I still didn't trust that a short circuit can never occur. I cut a small rectangle from a business card and taped it to the top surface of the USB-B connector on the Arduino Uno. Then I confirmed there was no short using a multimeter.