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I am a noob regarding electronics. I want to create a device for my bicycle using a GPS with an eByte E32 (a 1W LoRa SX1268 433MHz radio transceiver) and some batteries. The device will be in the seat post.

Will the RF transmitter work or it will create something like a "Faraday cage"?

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  • \$\begingroup\$ Please clarify what module it is, with link. Maybe passion-radio.com/tracker/lora-module-dx-889.html ? If so, you misspelled the name. The antenna choice and placement is probably more important, though. If you wish to leave the device attached to the bike for more than hours at a time, making the battery last long enough will be a challenge. \$\endgroup\$ Nov 18 '19 at 14:03
  • \$\begingroup\$ Thank you for your answer! This is the link: ebay.to/2poJ78S. If you feel that I can use something better, please tell me as I think I need just a simple beacon. I want the autonomy to be at least 1 month. I want all of the device to be inside the seat post. What do you mean by antenna choice and placement? Can you give me more details, please? \$\endgroup\$
    – Dacomis
    Nov 18 '19 at 14:53
  • \$\begingroup\$ is the post of carbon fiber? if not, acquire a bike with carbon fiber frame. That will be more likely to be stolen, so you can test your idea. \$\endgroup\$ Nov 18 '19 at 14:59
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This is a surface-mount RF module, so you need to make a PCB to solder it on, unless you do some freestyle wire soldering. You also need an antenna, a GPS module, a microcontroller, voltage regulator and battery.

For the device to run from a reasonable battery for a month, will take a strategy on when to power on the RF module and the GPS, and even to take the MCU into power-save mode. Careless design of the electronics easily adds unwanted currents that can reduce your battery time a lot.

As an example, assume you want a 1000 mAh 3.7V battery (about 20 grams). A month of battery time is 720 hours, giving you a power budget of 1.4 mA on average. As comparison, a GPS often draws 15 mA. When your RF module listens it draws an additional 14 mA and when sending, it will briefly draw 650 mA. Plus the MCU. Maybe you can fit a battery 10 times this size, at 200 grams. That eases the engineering but you still have to consider the power draw.

As you categorize yourself as a 'noob' with electronics, I'd humbly suggest this is an advanced project that you need to develop in multiple stages as you learn more of the topics involved.

A Particle or Pycom development board could help you accelerate the process by providing built-in RF, microcontroller and easy addition of a breakout GPS module. Still, this doesn't solve the power problem.

As for your question on RF shielding, if the antenna (not the module itself) is enclosed in or even close to metal, the RF properties will be affected. Unfortunately even carbon fiber is conductive so it suffers the same disadvantage. You might be able to place the antenna in some clever location, connected via a thin coaxial cable as antennas often are.

The boring answer is I'd look for some ready-made solution if you want to go cycling anytime soon.

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  • \$\begingroup\$ Thank you for this complex answer! \$\endgroup\$
    – Dacomis
    Nov 19 '19 at 7:12

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