I am thinking of making my own UHF tracking transmitters for a wildlife study.

Could I just connect a low power microcontroller to the Vcc part of this circuit http://www.instructables.com/id/Tiny-UHF-Tracker-Transmitter/ (e.g. Attiny85) and program it to turn the transmitter on after 10 days for a couple of hours every afternoon only (i.e. during the time when I'm searching for the transmitters)?

Or are there other considerations I haven't thought of here. I'm very unfamiliar with radio. If someone has other suggestions on how to significantly increase the battery life that would also be useful. I need to keep everything less than 2g (lighter is better).

My plan is to also have a temperature sensor and store temperature data on the Attiny. The main purpose I have for the transmitters would be to find the animals at the end of the study to retrieve the sensors rather than to track the animals so it would not need to be working continuously.

Possibly this is an obvious question and it would work fine, but it will be a lot of work so just wanted other opinions in case someone can see that it won't work or can suggest a simple and better way to increase the battery life.

Really appreciate any help, thanks!!

  • \$\begingroup\$ p.s. sensors will fall off the animals eventually anyway if they are unretrieved \$\endgroup\$ – shara Mar 7 '18 at 2:29

Yes - a microcontroller will allow you to save much energy and give you fine control over the whole operation.

You could get much improved range (or energy efficiency) if the radio used better modulation than OOK, for example LoRA (RFM95).

You did not say the exact range you need. There are some really tiny modules that contain everything (MCU + radio + antenna). Examples: SP1ML, BL-652.

The main challenge I see is the battery. A CR2032 battery weight 3 grams alone.

  • \$\begingroup\$ thanks! yes I'm also trying to find something which I don't actually have to completely build, so interested in suggestions for that also. I will probably try to use BR1225 which is about 1g but much lower capacity. 400m would be ok but larger would be better, I will probably track several species of bats, some have a 10km range and some 1km. \$\endgroup\$ – shara Mar 7 '18 at 8:59
  • \$\begingroup\$ devzone.nordicsemi.com/b/blog/posts/nrf52840-long-range-demo of course the better antenna, the better the range. \$\endgroup\$ – filo Mar 7 '18 at 9:48
  • \$\begingroup\$ wow, that looks cool (nrf52840), just not sure how to learn how to program it all quickly (since I'm really supposed to be studying bats) was also looking at this one docs-apac.rs-online.com/webdocs/1100/0900766b81100318.pdf \$\endgroup\$ – shara Mar 7 '18 at 22:10
  • \$\begingroup\$ main problem is I need to find some instructions on how to connect up a low power transceiver and get it running to do simple things with a microcontroller in a few hours rather than taking a week or two \$\endgroup\$ – shara Mar 7 '18 at 22:19

Using a microcontroller to make a low power timer is a standard thing to do.

Note that there are several techniques to reduce the microcontroller power, all of which can be found with the use of your favourite search engine. These include

a) choose a microcontroller which has app notes describing how to run at very low power
b) use a low voltage
c) use a slow clock (kHz not MHz)
d) leave the microcontroller in sleep for most of the time with only the RTC running

  • \$\begingroup\$ e) shut the microcontroller down leaving only the WDT running. \$\endgroup\$ – Jasen Mar 7 '18 at 8:55

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