Pre-certified module for short-range transmission of 1-bit signal

[pylo]

Hi!

I'm in need of something for my next project and I'm looking for some help, given that I lack the needed experience.

What I'd like to do is transmit an ON/OFF signal (just a single bit of data) to 1-2m distance at most, in a single direction (only one party sending). There is no need for any security whatsoever, this is a  completely non-critical application security-wise.

While it might be relatively easy to hack together something like this at home, I need this for a future product. As this would constitute an "intentional radio emitter", certifications down the road (FCC, RED, etc.) would be much too cost-prohibitive and unfeasible (I guess/think?) for a home-brew solution. I was hoping somebody here knows a pre-certified module, such as those available for BT or WiFi where certifications later on are greatly simplified, only, you know, simpler. Something like a dumbed-down wireless garage opener (with shorter distance and no security).

One option is of course to take a pre-certified module for a more complicated "technology", such as a bluetooth, and use that, but that is totally over-engineered for my needs. Well, it could be plan B (if everything else fails) actually, but I was hoping there is a module that is closer to my "barbaric application", as that is potentially both cheaper and smaller (I need size to be small).

Or maybe somebody knows a 3rd solution that could fit me?

Thanks for your help.

[sokoloff]

I'd start by looking at the 433MHz band transmitters; should work fine here, depending on the data rate. (I'm assuming from the question that the data rate is quite low, on the scale of human button pushes, but you didn't state explicitly.)

[pylo]

I'd start by looking at the 433MHz band transmitters; should work fine here, depending on the data rate. (I'm assuming from the question that the data rate is quite low, on the scale of human button pushes, but you didn't state explicitly.)

Exactly, it is actually for button pushes. Meaning I have no requirements for data rate (ok, let's make it 5bits/sec), but the action should be conceived as "instantaneous", so I do have a latency requirement (something around or below 50ms is ideal, but I guess that's not a problem).

[wraper]

What I'd like to do is transmit an ON/OFF signal (just a single bit of data) to 1-2m distance at most, in a single direction (only one party sending).

Sounds like it doesn't need to use radio to begin with. Usually IR is used for something like this.

[pylo]

Sounds like it doesn't need to use radio to begin with. Usually IR is used for something like this.

It needs radio, because there will be no direct line-of-sight between transmitter and receiver.

[Nusa]

How about audio? Whether it's within the human range of hearing is up to you.
A cellphone app could do that if you pick the right frequency and you wouldn't need to build a transmitter.
A dog whistle would be another version of an audio transmitter...extremely cheap, too.

Of course a cellphone app could also do bluetooth or wifi, so there's a prebuilt certified radio solution there as well.

[pylo]

I'd start by looking at the 433MHz band transmitters...

I'm still looking into these, but a search on Google and DigiKey mostly turned up modules that were either considerably larger or more expensive than some BT modules I've used in the past. One that could be promising though is Quasar's QAM-TX3, but from the looks of it it only got CE approval. I'll be contacting them tomorrow though for more information.

How about audio? Whether it's within the human range of hearing is up to you.
A cellphone app could do that if you pick the right frequency and you wouldn't need to build a transmitter.
A dog whistle would be another version of an audio transmitter...extremely cheap, too.

Of course a cellphone app could also do bluetooth or wifi, so there's a prebuilt certified radio solution there as well.

Nice thinking out of the box! My application does not lend itself to smartphone-use, but still, using a piezo tweeter and a suitable mic (any one from here for example) might just do the trick. And the product wouldn't even qualify as an intentional radiator   I do can think of a few possible troubles, like the processing power needed at the receiver (it is battery-operated) or how it affects pets. Nevertheless, I think this is worth inspecting.

[mark03]

Re: audio, you could in theory do the transmit side without electronics.  That's how the original television remote controls worked.  They were acoustic (ultrasonic) devices where a button press would strike a tuning fork.  Batteries not required!

[ThomasDK]

I'd start by looking at the 433MHz band transmitters...

I'm still looking into these, but a search on Google and DigiKey mostly turned up modules that were either considerably larger or more expensive than some BT modules I've used in the past. One that could be promising though is Quasar's QAM-TX3, but from the looks of it it only got CE approval. I'll be contacting them tomorrow though for more information.

433 MHz is an EU only band, you need different frequencies for other parts of the world. If you want a single world wide frequency, go for the 2.4GHz band. Zigbee or BLE is probably the cheapest options these days for something pre certified.

Another option could be MRF89XAM8A (EU) and MRF89XAM9A (US/Canada).

[Nusa]

Re: audio, you could in theory do the transmit side without electronics.  That's how the original television remote controls worked.  They were acoustic (ultrasonic) devices where a button press would strike a tuning fork.  Batteries not required!

I remember those. But children, which I still was at the time, were the original remote controls. For some stations (there weren't that many), we needed to adjust the rabbit ear antennas after changing the channel.

[soldar]

What I'd like to do is transmit an ON/OFF signal (just a single bit of data) to 1-2m distance at most, in a single direction (only one party sending). There is no need for any security whatsoever, this is a  completely non-critical application security-wise.

Sounds like a remote garage door opener or ceiling fan control would work. You can get those for close to nothing.

[macboy]

Look up "24YK-RX" and "24YK-TX".  They are around $1 each module. These are a transmit and receive pair of modules which do all the work for you. It doesn't get simpler, and you couldn't build it cheaper.

For the Tx, you supply power (3 V coin cell works great) and 1 to 6 buttons. Quiescent current is so low you simply keep the Tx powered all the time. The Rx module has six outputs corresponding to the buttons. It can be set up to toggle or normal mode. In normal mode, each output is on (active high) when the corresponding button is pressed. In toggle mode, each button press toggles the output. Each Rx can be paired to more than one Tx; the Tx sends the identity of the Rx so that other Rx modules will ignore the signal. That does not make it secure, but it makes them able to coexist with other modules without interference. The Tx and Rx modules are superficially identical and are actually transceivers, not simply transmit/receivers.

[splin]

Look up "24YK-RX" and "24YK-TX".  They are around $1 each module. These are a transmit and receive pair of modules which do all the work for you. It doesn't get simpler, and you couldn't build it cheaper.

How does this address the OP's primary requirement?

I was hoping somebody here knows a pre-certified module, such as those available for BT or WiFi where certifications later on are greatly simplified, only, you know, simpler.

To what extent does pre-certification reduce the cost of certification of the complete poduct given that emissions can be affected by factors external to the module such as the power supply, wiring and especially software in the case of more sophisticated modules? It should greatly improve the chances of passing the tests first time but is a simplified test procedure allowed when using pre-certified modules?

Does the same apply in Europe? I'm guessing you are not allowed to self-certify as you are for the CE mark?

[Lord of nothing]

433 MHz is an EU only band

Wrong!

[TheSteve]

Digi xbee's are gold, but likely way out of your budget.

[jmelson]

On eBay, you can find "4 channel remote" devices.  They have a little key-fob transmitter with 4 buttons and a little PC board with 4 outputs.  We cut these apart and put them into our own control modules.  They were about $4 each from China.  Here's the exact one we used :
https://www.ebay.com/itm/4-Channel-315MHz-Remote-Control-Receiver-module-Decoder-SC2272-M4/301694945179?hash=item463e6b879b:g:CwMAAOSwd0BVsKau:sc:USPSFirstClass!63130!US!-1:rk:6:pf:0

Now, these turn on one output while the button is pressed, so you'd need to add some kind of on/off latch to get your <whatever> to toggle on/off as desired.

Jon

[splin]

On eBay, you can find "4 channel remote" devices.  They have a little key-fob transmitter with 4 buttons and a little PC board with 4 outputs.  We cut these apart and put them into our own control modules.  They were about $4 each from China.  Here's the exact one we used :
https://www.ebay.com/itm/4-Channel-315MHz-Remote-Control-Receiver-module-Decoder-SC2272-M4/301694945179?hash=item463e6b879b:g:CwMAAOSwd0BVsKau:sc:USPSFirstClass!63130!US!-1:rk:6:pf:0

Are these pre-certified as required by the OP?