prairiedog
Advanced Member level 4
The best (discrete) IR remote-control receiver I have ever used, a Hitachi design from an old JCTV-3100. Fantastic range over 50m and used in large halls, works with IR bouncing off many surfaces :thumbsup:
I duplicated the circuit on a PCB. Works but it is oscillating at around 58kHz, and does pick up AM radio. It has a fair bit of noise and is very sensitive- putting a grounded probe near Q2 can lessen the oscillations. Putting a finger inches anywhere near the front-end it picks up interference. A wire mesh covering the photo-diode stops the AM radio ingress. A metal shielded enclosure, like the original has helps but it is still baffling me with the 58kHz. The transformer is tuned to 38kHz.
Adding a 68pF cap across C-B on Q4 stabilizes (fixes) the circuit but also lowers sensitivity (at 38kHz). This is the best I could come up with.
Any ideas how to tame the bandwidth and stabilize the circuit? The PCB has a ground-pour on both sides and does not seem to be the problem, and power is clean, 9V battery gives same results.
**broken link removed**
I duplicated the circuit on a PCB. Works but it is oscillating at around 58kHz, and does pick up AM radio. It has a fair bit of noise and is very sensitive- putting a grounded probe near Q2 can lessen the oscillations. Putting a finger inches anywhere near the front-end it picks up interference. A wire mesh covering the photo-diode stops the AM radio ingress. A metal shielded enclosure, like the original has helps but it is still baffling me with the 58kHz. The transformer is tuned to 38kHz.
Adding a 68pF cap across C-B on Q4 stabilizes (fixes) the circuit but also lowers sensitivity (at 38kHz). This is the best I could come up with.
Any ideas how to tame the bandwidth and stabilize the circuit? The PCB has a ground-pour on both sides and does not seem to be the problem, and power is clean, 9V battery gives same results.
**broken link removed**