Cheap RF 433MHz modules at more than 5volts?

Hi everybody, I'm toying around with a few 433MHz RF modules, these ones: http://www.ebay.it/itm/140847542952?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649 Using the VirtualWire library makes running those modules a joke :-)

I'm wondering if I can power the TX modules at more than 5V, let's say 9Volts, in order to increase TX range. As you may have seen, the eBay seller states it runs at 3V-12V, and I guess pumping up the voltage source may increase the output signal. But what happens to the input channel. I'm currently feeding a signal from Arduino, I don't know how VirtualWire codes the digital signal to be sent to the TX module (I guess it's a simple 0V-5V/off-on sequence). Anyway, does increasing the power supply of the TX module influence the way the data channel has to be controlled? Just to be clear: is it safe to power the TX module with +9V and still feed 0-5V digital signals from an Arduino pin?

Cheers, Roberto

I’m wondering if I can power the TX modules at more than 5V, let’s say 9Volts, in order to increase TX range.

I have not seen a datasheet to check if this would increase RF power but normally countries only allow these free spectrum devices to work up to a specific output power and this may be fixed within the chip. Using a well positioned matched antenna can make a lot of difference to range.

"Just to be clear: is it safe to power the TX module with +9V and still feed 0-5V digital signals from an Arduino pin?" If the device supports 12V, then yes. More power for the amplifier, separate from the input stage.

CrossRoads: "Just to be clear: is it safe to power the TX module with +9V and still feed 0-5V digital signals from an Arduino pin?" If the device supports 12V, then yes.

Ok, so it's safe, reassuring :-)

More power for the amplifier, separate from the input stage.

But I should use a common GND, right?

Still, does the TX module expect to receive an "amplified" data signal too? I'm sorry if I look naive but ... I'm still sending data from an Arduino pin which is calibrated on a 0-5V range, so I just want to be shure (I'm already pretty shure but I'm not an expert) that I don't need to change the signal voltage level, that if I keep it on a 0-5V range the TX module will be ok with that.

Yes, all grounds need to be connected.

“Still, does the TX module expect to receive an “amplified” data signal too?”
No, it still expects 0-5V signal.

CrossRoads: Yes, all grounds need to be connected.

"Still, does the TX module expect to receive an "amplified" data signal too?" No, it still expects 0-5V signal.

Thank you Man, you're always quick and spot-on, that's comforting :-)

I do what I can 8)

Riva:

I'm wondering if I can power the TX modules at more than 5V, let's say 9Volts, in order to increase TX range.

I have not seen a datasheet to check if this would increase RF power but normally countries only allow these free spectrum devices to work up to a specific output power and this may be fixed within the chip.

Presumably, the transmitter radiates the maximum legal ERP at 12V. At lower voltages, it probably radiates less.

I couldn’t follow the link to see what the modules were, but if they were like the FS1000A/XY-MK-5V ones I got, upping the voltage definitely helps, with a caveat.

In my experience, it didn’t do any good going using the voltage through one of the Arduino pins (e.g., Vin). Running it just off the Arduino at 5V (via USB), I would get a range of about 6ft/2m. If I plugged a 9volt battery into the Arduino and still fed the transmitter via Vin, there was no improvement in range. If I powered the transmitter directly from the 9v battery, the range increased to more than 30 feet/10m.

Bob

Did you add a 17cm antenna wire? That should make a big difference.

I think this is the product that robitabu is referring to:

http://www.ebay.com/itm/PCF10-FS1000A-433-MHz-Wireless-Radio-Transmitter-/230869801124

Ok, I see a pad for an antenna - try putting a 17cm piece of wire on it. Simple 30 guage wirewrap wire is all you need.

tylernt:

Riva:

I'm wondering if I can power the TX modules at more than 5V, let's say 9Volts, in order to increase TX range.

I have not seen a datasheet to check if this would increase RF power but normally countries only allow these free spectrum devices to work up to a specific output power and this may be fixed within the chip.

Presumably, the transmitter radiates the maximum legal ERP at 12V. At lower voltages, it probably radiates less.

No such guarantee - the 433MHz and other ISM bandplans differs from territory to territory, and in particular I recall the max duty cycle and max power vary across these band in very specific ways - it is your responsibility to stay within the limits for your territory.

I see this is a very old thread, but I had the same range problem with mine. So, I selected an unused Ardunio pin and drove it with the Tone() command. I think it was at 1kHz. Added a couple of diodes and caps to make a voltage doubler. (for testing I also did a two stage doubler to make it near 14 volts - which was out of speck, but at the cheap cost I thought its ok if I blow it. It was good).

I also added the antenna as well got the whole thing as high off the ground as I could reasonably do. (to avoid grand losses.) All done, I got the range range above 150 ft.

I also considered making a parabolic reflector or Yagi antenna, but I didn't need it.

Just for fun I also swapped out several receivers and they all had quite a bit of difference in sensitivity (all using the 17 cm antenna). I was surprised.

As a couple final steps, I added some filters between the receiver module and the power off the receiver Arduino, and added some long lines connecting the two to get the receiver as far away as I could from the Arduino.

For something is simple, they can be made to work very well.

Nice job with the testing. I run mine from a LiPo (3.7 to 4.2V) and see 50 feet no problem (one end of my fencing club to the other) with 17cm antennas.

Transmitter is LiPo powered, Receiver runs from 5V.