The MX-RM-5V breakout board is the European 433.92MHz version, and the RF-5V is the US 315MHz version.
The board is sometimes labeled XY-MK-5V.
It is primarily used in remote control solutions.
Design Flaws
This receiver has a very simple receiver architecture: an oscillating L-C circuit is connected to a LM358 OpAmp. Receiving a signal drives the OpAmp into saturation.
While sensitivity is reasonable, selectivity is not. This receiver is easily jammed by strong signals, even when these signals are transmitted on a completely different frequency.
For example, when a device closer than 20cm to this receiver emits a WiFi signal, then this can be enough to render this receiver unusable: it won’t pick up any legit signals anymore.
It may in fact be enough to mount this receiver close to a large capacitor to deafening it.
Receivers based on advanced receiver chips such as SYN470 or SYN480 are much more reliable.
Versions
Two versions exist:
- 315MHz (US market): this board is marked RF-5V on the back side. On the front side, a big 0.5W resistor is soldered on the board.
- 433.92MHz (European market): this board is marked MX-RM-5V on the back. There is no big resistor soldered on the front side.
Pins
The board exposes four pins that are labeled on the back:
| Pin | Label | Description |
|---|---|---|
| 1 | GND | negative voltage |
| 2,3 | DATA | Data Out |
| 4 | VCC | 5V |
Make sure the power supply is properly filtered and carries no exceptional noise which could interfere and distort reception.
Antenna
This receiver can be operated without an antenna (which limits reception to just a few meters). For better reception, an antenna must be soldered.
Here is how to create a simple coil-loaded antenna.
The antenna needs to be soldered to the unmarked through-hole connector on the lower right edge of the board, next to the inductive loop.
Make sure your board has a soldered copper inductive loop has three windings. There have been reports of partially incorrectly assembled boards that use the eight winding coils designed for the transmitter board.
Technical Data
| Item | Description |
|---|---|
| Voltage | 3-8V, 5V preferred |
| Current fully operational | 4mA |
| Frequency | 315MHz or 433.92MHz |
| RX Sensitivity | -105dBm |
| Modulation | ASK (AM) |
| Data rate | <10kbps |
| Distance | few feet (w/o antenna), 30-50m (with antenna) |
| Size | 30.3x13.8x7mm |
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(content created Apr 18, 2024)