I’m working on integrating a nrf24L01 in to a steering wheel with the intent to relay signals from steering wheel mounted controls to the rest of the vehicle. The steering wheel is removable (for the driver getting in and out) and is the driving force behind all of this.
I originally rigged a plastic project enclosure (with uC and nrf24l01 in it) to an old steering wheel and hooked up the controls and it worked very well for several hours of driving.
However, when I placed it inside the steering wheel the reliability seemed to drastically go down. The only thing I can believe that may have caused this other then the carbon fiber would be possible damage to the circuit board when moving it, but initial inspection didn’t show anything obvious
Does anyone know how carbon fiber affects the transmission of wireless signals? Most notably in the 2.4-2.5GHz range?
The receiver is mounted behind an aluminum .048 thing dash plate and about 2’ away (pessimistic estimate). So, the signal must travel through about 4 layers of carbon fiber and .048" thick aluminum to a small duck antenna mounted in the dash.
The way your post is written, it sounds like you are trying to transmit through the Aluminum sheet. If so, that is your problem, not the carbon fiber. If this is not the case, then the Carbon fiber is your culprit. It is used to absorb RF in the stealth aircrafts with great success. One of the tests that works very well for RF absorption is sticking the item in question in the microwave oven for a few seconds. If it gets warm to the touch, it is very lossy in the 2 GHz range. Anyone who has stuck a CD ROM disk in the microwave, can attest to the spectacular demonstration of RF absorption. (Oh, by the way…don’t try this at home!)
There is a move going on towards 2.4 GHz in the radio control world (aircraft, boats, cars) and it seems that receivers in carbon (planes) have very big issues.
Probably, if you can keep the antenna outside the CF stucture, it only then will work well.
I vote for the CF causing your problems too. I know in a lot of (full-size) aircraft that have carbon fiber bodies, they usually have a section that is glass fiber only where you can mount your radio, GPS, transponder, ELT, etc. I know CF kills GPS and that’s somewhere around 2.4GHz.
Actually GPS is about 1.5GHz, but close enough to have similar responses. Carbon fiber is highly conductive, so you’ve essentially put your antenna inside a Faraday cage.
SOI_Sentinel:
Actually GPS is about 1.5GHz, but close enough to have similar responses. Carbon fiber is highly conductive, so you’ve essentially put your antenna inside a Faraday cage.
I wasn't even close... thanks for the correction. Gotta remember to google before I post.
The National Institute Of Standards (NIST) did an expensive and extensive measurement campaign on the attenuation of common construction materials vs. Freq. Not sure carbon composite is in there, but maybe something close.