I have written my own basic IR protocol that is using an ATtiny85 to send packets over to an arduino via 6 940mm IR leds.
The whole thing works...but before I take it outside, I want to extend it's range.
From the current useage, the 6 LEDs was the best I could come up with for the transmitter.
On the Rx side, can I use more than one photodiode, in parallel, to increase the device's sensitivity?
I figured as for resistors in parallel, if 1/Rt = 1/R1 + 1/R2 + 1/R3 ...
Then the resistance decreases much more than with just the one photodiode. Also having multiple ones gives more area coverage (I am thinking a sort of small mirror dish as well to reflect on the them).
The best approach to increasing sensitivity is to use the proper IR bandpass filter in front of the photodiode, and a photodiode amplifier. See the attached pdf for amplifier schemes.
jremington:
The best approach to increasing sensitivity is to use the proper IR bandpass filter in front of the photodiode, and a photodiode amplifier. See the attached pdf for amplifier schemes.
Awesome thanks!
No idea why I did not think of simply using an OPAMP....ooops.
I have an IR pass thingy. It seems to work, I can see the IR leds through it using my mobile phone camera but nothing else (visible). It does seem to help so yeah...hopefully I will enclose the whole RX circuit behind the IR filter thingy and then just drill a hole for the USB cable to attatch to the PC/Raspberry Pi for power and Serial Comms :).
The best detector circuit will depend on the transmitter bandwidth - high speed detection
rather forces use of reverse biased mode and a suitable high amplifier. At low bandwidth
just the self-voltage of a photodiode can be used I think - this is very high impedance
and probably requires filtering out of non-IR light to get a good dark to light current ratio.
The other approach to improving sensitivity is using optics - lens and parabolic mirrors.
Then the resistance decreases much more than with just the one photodiode. Also having multiple ones gives more area coverage (I am thinking a sort of small mirror dish as well to reflect on the them).
Thanks!
Improving the reception using more diodes will also increase the noise.
Better to use optics or increase the transmission power.
Edit
A simple way is to mount the receiver diode at the focus of a torch reflector.
Acceptance angle is fairly narrow though.
Boardburner2:
Improving the reception using more diodes will also increase the noise.
Better to use optics or increase the transmission power.
Edit
A simple way is to mount the receiver diode at the focus of a torch reflector.
Acceptance angle is fairly narrow though.
Thanks, just gutted an old (really bad single LED) torch. I can drill a hole in the PCB that held the LED I think and just glue gun the photodiode in its place :).