How to find a right RF module for a project?

In summary: That way, the pinging will only happen when it's really necessary.In summary, Bluetooth Low Energy (BLE) may be a better option for this application.
  • #1
rushi121
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I am a product developer but not an electronics engineer. I am doing a cost analysis of a product idea for my company. The product will need something like this...

There will be two small portable devices (A and B) 1 meter apart (not in line of sight since A can be in pocket). Product A will keep pinging product B at regular intervals. When pinged, B will send response to A for that ping. A knows that B is still available.

Now, if we move B away from A (e.g. > 3 meters) and if A pings B and since B is out of range, A will not get response from B. In such case A will sound an alarm.

I know we can do device to device communication using RF modules. But I don't know which module or protocol to use for this.

My questions (Please answer considering that I am not prototyping but actual product for market):

  • Which protocol and module to use?
  • Can you point me to any module available in market that I can look into?
  • Since A will be pining B at regular interval, will that module drain battery much? If yes, how much long will battery last approximately?
  • Any existing product in market you can think of that does something similar (pinging at regular intervals)?
  • Do I need a micro controller?
 
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  • #2
rushi121 said:
I am a product developer but not an electronics engineer. I am doing a cost analysis of a product idea for my company. The product will need something like this...

There will be two small portable devices (A and B) 1 meter apart (not in line of sight since A can be in pocket). Product A will keep pinging product B at regular intervals. When pinged, B will send response to A for that ping. A knows that B is still available.

Now, if we move B away from A (e.g. > 3 meters) and if A pings B and since B is out of range, A will not get response from B. In such case A will sound an alarm.

I know we can do device to device communication using RF modules. But I don't know which module or protocol to use for this.

My questions (Please answer considering that I am not prototyping but actual product for market):

  • Which protocol and module to use?
  • Can you point me to any module available in market that I can look into?
  • Since A will be pining B at regular interval, will that module drain battery much? If yes, how much long will battery last approximately?
  • Any existing product in market you can think of that does something similar (pinging at regular intervals)?
  • Do I need a micro controller?
Sounds like a good fit for Bluetooth Low Energy (BLE): https://en.wikipedia.org/wiki/Bluetooth_low_energy

:smile:
 
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  • #3
Number of issues:

1. What happens when other pingable devices are nearby
2. How precise do you want the distance
3. Do you want sender and receiver factory paired? Can they be re-paired to different devices?
4. Is there any significant data transfer beside the ping.

One issue with bluetooth is that the pairing process is never simple and can be problematic.

One of the big problems is designing a timed protocol ( synchronized timing windows) such that the devices know when to turn on to ping. If the receiver is on all the time that is way too much power.
You will definitely need a microcontroller based solution for a robust commercial solution. The controller can be in the RF chips (depends on what you really want to do)

Bluetooth may be overkill. More suitable might be the chips like those used in wireless mice.
Anyway, these guys build Bluetooth and very low power non-bluetooth and their sales/applications support should be able to help you decide.
http://www.nordicsemi.com/eng/Products/2.4GHz-RF
 
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  • #4
With RF anything over a few 100 millimetres you would be looking in the UHF range, and there are certifications that need to be considered depending on your target market countries.
This type of system is often used, in reverse I suppose, in mining environments where personal and small vehicles would carry transmitters, and larger mining vehicles would carry receivers with alarms to alert them when there are people about. They're generally marketed as "Collision avoidance systems"
In your case the person would carry the buzzer part and receiver, while I'm not very familiar with the electronics side of it, I think you may struggle to manufacture a pocket sized receiver, unless it has a little aerial sticking out.
 
  • #5
meBigGuy said:
One of the big problems is designing a timed protocol ( synchronized timing windows) such that the devices know when to turn on to ping. If the receiver is on all the time that is way too much power.

----------------------------

For timed protocol I will turn on and off pinging based on a switch. It won't be on most of the time. But I was thinking about how BLE Beacons work and they continuously ping and battery last from 6 months to 2 years. Can't we do something similar or are they something special?
 
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  • #6
BLE can probably do what you want, but I don't know the subtleties of pairing, and I don't know know your real requirements in that regard.
You should talk to Nordic, then TI.
 
  • #7
This might be a good place to start.
https://www.nordicsemi.com/eng/Products/Bluetooth-Smart-Bluetooth-low-energy/nRF51822-Bluetooth-Smart-Beacon-Kit

But, be sure to understand the heck out of the pairing issues before you start.
 

Related to How to find a right RF module for a project?

1. What is the frequency range of the RF module I should choose?

The frequency range of an RF module is an important factor to consider when selecting one for your project. It is usually listed in the product specifications and is typically measured in megahertz (MHz). The frequency range you need will depend on the specific application and the environment in which it will be used. For example, if you are working with wireless sensors, a lower frequency range (i.e. 433MHz) may be more suitable for longer range transmission. On the other hand, if you need to transmit data at higher speeds, you may need a higher frequency range (i.e. 2.4GHz).

2. What is the transmission distance of the RF module?

The transmission distance of an RF module is another important consideration. It refers to the maximum distance at which the module can effectively transmit and receive data. This distance can vary greatly depending on the specific RF module and its surrounding environment. Factors such as obstacles, interference, and signal strength can all affect the transmission distance. It is important to choose an RF module with a transmission distance that meets the requirements of your project.

3. How much power does the RF module consume?

The power consumption of an RF module is an important factor to consider, especially for battery-powered projects. It refers to the amount of energy the module uses while transmitting and receiving data. This can vary greatly depending on the specific module and its operating frequency. It is important to choose an RF module with a power consumption that is compatible with your project's power source.

4. What type of modulation does the RF module use?

The type of modulation used by an RF module is another important factor to consider. Modulation refers to the method of encoding data onto a carrier wave for transmission. The most common types of modulation used in RF modules are Amplitude Shift Keying (ASK), Frequency Shift Keying (FSK), and Phase Shift Keying (PSK). Each type has its own advantages and disadvantages, so it is important to choose an RF module with a modulation type that is suitable for your project's requirements.

5. Can the RF module be easily integrated into my project?

The ease of integration is an important consideration when choosing an RF module. Some modules may require additional components or programming to function properly, while others may be more plug-and-play. It is important to choose an RF module that is compatible with your project's microcontroller or other components and has clear documentation or support available to help with integration.

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