7
\$\begingroup\$

I am using some "no-name" (in fact "XY-MK-5V" stands on the board) 433 MHz receiver (and transmitter) on an Arduino project. I can receive the signals sent from my other Arduino very good (it sends with 12 V as mentioned in another question).

The problem is: I want to receive signals from other parts - such as simple power outlets wireless switches, too. When they are sitting next to my Arduino, everything is fine. When they are ~ 3-4 m away, the Arduino gets no signal (or more times doesn't get the right signal).

At that time I am using a simple ~17 cm long wire that is curly to save space soldered to the "antenna port".

What can I change in order to get a better signal?

\$\endgroup\$
  • 1
    \$\begingroup\$ Straighten out the wire. That way, it will be 1/4 wavelength long and have maximum gain at 433 MHz. The first rule about good reception is to have a good antenna. \$\endgroup\$ – Dave Tweed Mar 23 '14 at 0:33
  • \$\begingroup\$ That didn't help. I heared of using some Coax Cable as antenna, do I connect the Ground to the common ground? \$\endgroup\$ – Tobi Mar 23 '14 at 0:42
  • \$\begingroup\$ Are you using AM or FM? What are the devices using? \$\endgroup\$ – Andy aka Mar 23 '14 at 1:04
  • \$\begingroup\$ Good Question... it is weather printed on my power sockets that are controlled by the remotes or the remotes themself. Also nothing on the tr/rx modules, I am using. How cah I check that? \$\endgroup\$ – Tobi Mar 23 '14 at 22:19
  • \$\begingroup\$ I might be worth adding a bit of background from your other questions that say what the transmitter actually is and how it's encoded / decoded, what the antenna is each end etc. \$\endgroup\$ – PeterJ May 10 '14 at 10:30
5
\$\begingroup\$

Are you sure that your module works well to 12 V?

Since it is the "XY-MK-5V" model I think it has the voltage up to 5 V as ideal.

For all I know, these modules work well between 3.3 V and 5 V, maybe saturating the circuit.

Really, the transmitter work with up to 12 V.

But I suspect that it does not work at the frequency in question. See, there are a lot of bad information on the Internet about them.

Transmitter XY-MK-5V

  1. Product Model: MX-FS-03V
  2. Launch distance: 20-200 meters (different voltage, different results)
  3. Operating voltage: 3.5-12 V
  4. Dimensions: 19 * 19 mm
  5. Operating mode: AM
  6. Transfer rate: 4 KB/s
  7. Transmitting power: 10 mW
  8. Transmitting frequency: 315 MHz
  9. An external antenna: 25 cm ordinary multi-core or single-core line

Receiver: XY-MK-5V

  1. Product Model: MX-05V
  2. Operating voltage: DC5V
  3. Quiescent Current: 4 mA
  4. Receiving frequency:315 MHz
  5. Receiver sensitivity:-105 dB

See more at: How to use 315 MHz RF transmitter and receiver modules with an Arduino

\$\endgroup\$
  • \$\begingroup\$ ... The Receiver says ...5V. That does not belong to the sender that workds with 12V also. More voltage more power. \$\endgroup\$ – Tobi May 10 '14 at 10:05
  • \$\begingroup\$ well, maybe not so direct rule thus further if u saturate the transistor output RF. But now tested and does not work, and make sure the transmitter, FS1000A stand such a strain without inconvenience. Well, I do not know what the output transistor, and what characteristics it. \$\endgroup\$ – Delfino May 10 '14 at 14:22
  • \$\begingroup\$ ![XY-MK-5V][buildcircuit.com/wp-content/uploads/2012/06/receiver-only.jpg] \$\endgroup\$ – Delfino May 10 '14 at 16:21
5
\$\begingroup\$

The frequency of the TX is stamped onto the cap of the SAW resonator. I have played around with these modules a lot and they are usually good for 100 metres line-of-sight. Only use a straight single core antenna, 173mm in length, and make sure your power supply is clean. The supply from an Arduino is OK but try adding a 10uF capacitor to the TX and RX module VCC and GND inputs.

I use VirtualWire 1.27 for all my packet sending and it works very well but for other devices they must send enough preamble bits for the RX to settle properly otherwise the Rx will never demodulate the data correctly and you will have all sorts of trouble decoding it. If you're just looking for carrier on/off coding you will find interference is your greatest enemy.

\$\endgroup\$
  • \$\begingroup\$ You got 100 meters of range in LOS from the cheap 433 MHz Chinese modules? I'm asking because I wasted today and I got nothing above 3 meters. Also using VirtualWire... \$\endgroup\$ – janosrusiczki May 24 '15 at 18:49
4
\$\begingroup\$

if you decrease the baud rate you increase the range, because the bits become longer in time. more time to decode is resulting in better natural resistance to spike interference.

This is true of any wireless digital system.

\$\endgroup\$
  • 6
    \$\begingroup\$ This is awfully thin for a SE answer. Can you explain why this is true? \$\endgroup\$ – Dave Tweed Mar 9 '15 at 11:49
  • \$\begingroup\$ at all, I cannot change stuff on the sending part \$\endgroup\$ – Tobi Nov 24 '19 at 1:18
0
\$\begingroup\$

Simple RF electronics. More power in = more power out. So if the unit is powered to it's threshold you will get more range.

Also consider adding a coil-loaded antenna to both the TX and RX. For the price these are brilliant little units.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.