Advice Needed 433Mhz Receiver

I have a project where we need to use a KeyFob to trigger an event on an arduino. This will then trigger an event on a PC. I would like the keyfob to trigger the event around 30 meters from the receiver. With the receiver inside a building.

My car seems to be able to do this!

The basic project is working but the KeyFob 433Mhz is a bit of a problem with distance.

We are only getting a few meters before the key fog button click does not trigger on the arduino.

So I need some advice on the products I have chosen.

I am currently using these products

KeyFob
http://www.ebay.com/itm/gib-315-433MHz-Handy-Key-ring-2-Channel-RF-Wireless-Remote-Control-Garage-Door-/171528692002?pt=LH_DefaultDomain_0&var=&hash=item27efe82122

433 Mhz Receiver

The receiver has these Technical Specifications:

  • Working voltage: 5.0VDC +0.5V
  • Working current:≤5.5mA (5.0VDC)
  • Working principle: single chip superregeneration receiving
  • Working method: OOK/ASK
  • Working frequency: 315MHz-433.92MHz, customized frequency is available.
  • Bandwidth: 2MHz (315MHz, having result from testing at lowing the sensitivity 3dBm)
  • Sensitivity: excel –100dBm (50Ω)

The keyfob specs say:

  • Working voltage: DC12V (27A/12V battery x1)
  • Operating Current: 10MA
  • Emission Distance: 20-50m (Open area)

From what I believe -100dBm is better than -114dBm? is this correct?

I have seen some 433Mhz receivers say that they are -114dBm - like here

I am using an external aerial with the receiver - like this

I have also seen that some keyfobs say they work 50-100m - see here

Do you think I am better to buy some of these?

How can I test the signal strength of a 433Mhz device other than clicking the button and seeing if it triggers on the arduino?

You might try a simple, 17 cm straight wire antenna. The impedance of the one you show may not be appropriately matched to the receiver. You could also try adding a wire antenna to the keyfob, which will require opening it up.

Most of the cheap receivers do not report signal strength.

If I read you post and the links correctly, the key fob is a dual channel device. Transmitting on 433 MHz on one channel and 315 MHz on the other.

You link for the receiver goes to an Ebay posting for both a receiver and transmitter, both on 433 MHz.

Your key fob may need to be programmed for the codes you desire, before it will transmit. That seems to be what the text of the link shows.

You can easily build a sensitive field strength meter that will give and indication of RF output from any of your transmitting devices. Google ""field strength meter".

By the way, my car key fob operates on 315 MHz and works from at least 100 FT.

Paul

The receiver you have is a superregen type which is the worst type you can buy.
Receiver sensitvity is measured in dbm with the smaller number the better, ie -114 dbm is much better than - 100 dbm.

mauried:
The receiver you have is a superregen type which is the worst type you can buy.
Receiver sensitvity is measured in dbm with the smaller number the better, ie -114 dbm is much better than - 100 dbm.

Thanks for the info - I have seen some other receivers

http://www.ebay.com/itm/Super-heterodyne-RF-Wireless-Receivers-Module-433-92-MHz-3-3V-5-5V-/271653722259?pt=LH_DefaultDomain_15&hash=item3f3fd2d893

Receive sensitivity of -115dBm

and

http://www.ebay.com/itm/Super-heterodyne-OOK-Wireless-Receiver-Module-Best-uk-Interference-433MHZ-116dBm-/321606974349?pt=LH_DefaultDomain_3&hash=item4ae144fb8d

Receive sensitivity of -116dBm

Paul_KD7HB:
If I read you post and the links correctly, the key fob is a dual channel device. Transmitting on 433 MHz on one channel and 315 MHz on the other.

The keyfob is 433 only - you can choose 433 or 315.