![\"\"](\"https:\/\/wonghoi.humgar.com\/blog\/wp-content\/uploads\/2021\/04\/433Mhz-1CH-RF-Relay-Receiver-Wireless-Remote-Control-Light-Switch-Front.png\")
<\/figure><\/li>![\"\"](\"https:\/\/wonghoi.humgar.com\/blog\/wp-content\/uploads\/2021\/04\/433Mhz-1CH-RF-Relay-Receiver-Wireless-Remote-Control-Light-Switch-Back.png\")
<\/figure><\/li><\/ul>Note that there’s a schematic picture which switched the colorings of the input and output pairs.
The actual wiring color is correct.<\/figcaption><\/figure>\n\n\n\nInitially I was tempted to get the built-in relay version, but I was worried about the current draw from 5Vsb and those are 12V relays., not to mention the footprint is much bigger (the one above is 22.5mmx 11mm x 8mm). <\/p>\n\n\n\n
I thought I can figure out with some sort of BJT switch instead of using a relay that has a much bigger current draw requirement, but I realized it’s a pain in the ass because the output is ‘floating’ differential. The OUT- does not tie to the power ground (it’ll short out the unit when I tried to. That’s why I added quotes to ‘floating’ because it’s only relative to OUT+). I also measured OUT+ which is +5V with respect to power ground. <\/p>\n\n\n\n
I tried to power a LED and it only works if current flows from OUT+ to OUT- so it’s really sinking current from source power to do that, and it’s unidirectional. <\/p>\n\n\n\n
I’d just take a gamble and hook up with a 5V NO relay that I have around. Turned out it actuates with the 5Vsb from the USB header. I glued the relay to the back of the PCB and hook up a flyback\/snubber diode (reverse biased) across the relay coil so the back EMF won’t fry my motherboard.<\/p>\n\n\n\n
![\"Image](\"https:\/\/i.ebayimg.com\/images\/g\/NfgAAOSwjFVfM1K4\/s-l1600.jpg\")
The transmitter switch costs $3.65, which is more expensive than the receiver board.
It comes with 12V battery which is typical with 433Mhz door bells.<\/figcaption><\/figure><\/li>![\"\"](\"https:\/\/wonghoi.humgar.com\/blog\/wp-content\/uploads\/2021\/04\/433Mhz-1CH-RF-Relay-Receiver-Wireless-Remote-Control-Light-Switch-Label.png\")
Press the learning button once and immediately press the transmitter button to pair<\/figcaption><\/figure><\/li><\/ul><\/figure>\n\n\n\n Seems like the transmitter-receiver pair is on momentary switch mode by default, so no addition configuration is needed other than pressing the learn button and immediately press the transmitter button to pair.<\/p>\n\n\n\n
I wired a jumper extension cable (male – female) to the relay output from the middle as a by-pass since I’d like to keep the original power switch’s functionality (so it’s basically OR-ing between hardwired switch and the wireless remote 433Mhz switch)<\/p>\n\n\n\n
![\"\"](\"https:\/\/wonghoi.humgar.com\/blog\/wp-content\/uploads\/2021\/04\/DSC_2684-1024x683.jpg\")
The white wire is the antenna<\/figcaption><\/figure><\/li> ![\"\"](\"https:\/\/wonghoi.humgar.com\/blog\/wp-content\/uploads\/2021\/04\/DSC_2685-1024x683.jpg\")
Basic pinouts<\/figcaption><\/figure><\/li> ![\"\"](\"https:\/\/wonghoi.humgar.com\/blog\/wp-content\/uploads\/2021\/04\/DSC_2687-1024x683.jpg\")
Bottom view<\/figcaption><\/figure><\/li> ![\"\"](\"https:\/\/wonghoi.humgar.com\/blog\/wp-content\/uploads\/2021\/04\/DSC_2688-1024x683.jpg\")
Note the reversed-biased diode soldered across OUT+ and OUT- as snubber for relay coil<\/figcaption><\/figure><\/li><\/ul> Close up for construction and the high level wiring.<\/figcaption><\/figure>\n\n\n\n Here’s an example of taking 5Vsb from USB header and tapping into the power switch jumper in Front-Panel jumper block:<\/p>\n\n\n\n
![\"\"](\"https:\/\/wonghoi.humgar.com\/blog\/wp-content\/uploads\/2021\/04\/DSC_2683-1024x683.jpg\")
<\/figure>\n\n\n\nNote that the PWR SW- pin is connected to the ground. Since I’m using a relay, the relay output is floating so the polarity does not matter. <\/p>\n
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