I would like to contribute to the list and create a PCB board layout to simplify making an RPM switch, but first I have to make a working one, and I'm a bit confused...

I've finally decided to give this a shot, and just need some clarification on the shematic. If you've made a working RPM switch or are good in this area, please take a moment to help.

I've attached two pics. One is the original found in the 2nd gen. archives, and one is my interpretation of the note at the bottom. This note at the bottom says "Feed 10k resistor on D1 from pin 9". This may sound nice and simple, but I'm not sure if D1 is still connected to pin 11 as I've shown in the second pic., which is my interpretation of the statement.

Have a look, and let me know if I edited the shematic properly. I have wired everything as shown, but ended up with lots of wires. Once I have a working prototype, I want to use a PCB layout program to simplify traces and such so that one can make this RPM switch very easily.

 

D1 needs to be connected to pin 11 to provide signal to the op-amp. Your modifications look correct.

Test on a breadboard first.

 

Thanks Aaron.

I jumped into this head first, and started soldering in parts into a perf. board. Since I'm obviously a noob at this, I ended up with a crapload of thin wires looping over the board because I didn't study all the traces needed. The next one will be much cleaner, as I've drawn footprints and connections in CAD. I will also try to use ferric chloride to etch copper (as found on the net) and make traces on the next PCB board. Any info on this and where to find chemicals around here?

 

Iron chloride, Google it or find a science supply store and ask. lol Ill ask my comp friends if they know anywhere to find it.

 

Ferric Chloride will be available at any good electronics store. That's a real electronics store, not Rat Shack. Though Rat Shack had it back in the day, they no longer stock it. May be special order but the kid behind the counter probably won't have a clue as to what you are referring to.

 

Thanks again. BTW, the local electronics store where I got the other parts from had it, including the boards (it truly is a real electronics store, with all kinds of crap).