JP1 Remotes

Tommy Tyler

New schematics (alas, no construction details) and trouble-shooting information have been posted here.

thilo · Joined: 10 Feb 2009 Posts: 1

Thanks a lot for the schematics. I'd like to build it but I'm not shure about
the capacitor and resistors. The drawing is a bit hard to read.

Just want to clarify figure 2:

C1 is 0.1µF (Zero is hard to read)
R1, R3, R5 4.7K
R2, R4 47K (or is it 4.7 and the points are missing?)

Just curious: why does figure 1 don't need a capacitor?
Thanks a lot
Thilo

Tommy Tyler · Posted: Tue Feb 10, 2009 10:39 am Post subject:

Those schematics are REALLY hard to read, terrible. Sorry for that. I just posted a new, easier to read version. Take a look.

As for the 0.1MFD capacitor, either the discrete transistor version or the IC version will work just fine with or without it. It's very common design practice to put a bypass capacitor on the Vcc line for high speed ICs, and I probably did it out of force of habit.

Kevin Timmerman · Posted: Mon Jan 25, 2010 11:48 am Post subject:

JP1 Flash interface using digital transistors. Minimal parts for small size and quick construction.

Digital transistors have a built in resistor divider network that allows them to be directly driven by digital voltage. The reverse BE breakdown is 10 volts, so RS-232 can be used directly on the base (charge pump transcievers output +/- 9V). An additional ordinary NPN is used to present a high impedance on the remote's tx line to allow the remote to operate normally with the interface connected.

madmalkav · Joined: 01 Sep 2011 Posts: 63

Any alternatives to that FJN3301R transistors? I'm unable to get them locally and only online supplier I found ask too much for shipping to Europe.