Hey, i found this link kinda interesting.. its not overly complicated, so i thought the newer electronics guys (or perhapse the more seasoned as well) might like it :P


Posted on 2003-05-03 20:56:32 by NaN
It appears this guy has alot of simple circuits to read about... ( http://www.epanorama.net/circuits/ )

Im impressed with one of them: http://www.epanorama.net/circuits/servo10v.html

I feel stupid for not seeing this solution myself when i was designing servo controls on my robot project in school. I did it the hard way (the hardest probably). I wrote all servo timing required internally in PIC asm (all software). This solution would have saved me alot of time!

:rolleyes: Its not like i didnt know of the 555 either! :rolleyes:

Sometimes its the simplest things that exceeds our focus.....


PS: Here is a good site on 555 Timers if you dont already know them... ( http://www.uoguelph.ca/~antoon/gadgets/555/555.html )
Posted on 2003-05-03 21:27:34 by NaN
Thx Nan,
very nice and useful links !
Posted on 2003-05-04 15:01:36 by Bit7
He he he... simple circuits work best!

We once built an 'Automated Train Braking System' model for an exhibit whose main circuit was a 555 timer in monostable configuration. Basically we just added little bits of wire on the model train's track, which would hit a probe at the bottom of our train, which would trigger the monostable, which would turn off the train until the monostable's time ended.

Well you see our prof once did a project like that too (when he was one year after our level then), except they used a PC to control it. So we took that as a challenge and built an even simpler implementation. Slightly hackish of course (I mean, those little bits of exposed wire looked real weird). Fun, really.
Posted on 2003-05-04 20:28:07 by AmkG
Little bits of wire? No photocells to detect the train's shadow?

Or even slice the running rails to detect the motor current as a certain spot.

(Can you tell I've done lots of model railroading?)
Posted on 2003-05-04 23:04:34 by Ernie
The 'model train' was, in fact, a little toy train with a circular track, the power supply to the train was *on the train* itself...

Otherwise we could have put the controlling unit on the tracks, and turn ofg the power supply to the tracks themselves.

So the control unit would have to be on the train itself (and of course, in a 'real-world' application, we don't want to shut down all the trains, just one train that is in one station, so we can't pull the plug from the tracks, only individual trains).

Our original plan was to put little IR LED's at each station and the train would have little photocells that would detect their presence. When the train was on a station, it would detect the LED's and stop.

However as it happens that would mean requiring a power supply on the tracks themselves. So to further simplify the design, we just plopped up some little bits of wire that would connect two probe lines (one grounded, one the true input line) when the lines brushed the wire.

Basically for 'retrofitting' reasons, we said to the profs that by adding a simple circuit to the train, and adding just little bits of wire to the tracks (and nothing else, no fancy-schmancy expensive IR LED's), we could (in theory, anyway) automate an *actual* electric train system.

We even used a relay instead of a transistor switch to turn the train's motor on/off since relays can tolerate higher currents than transistors (he he he 'real-world' consideration again...). 'Course we didn't know *** about how to *** handle the *** relay (e.g., we didn't know we had to put a diode across the relay coil when connecting it to a semiconductor device), and it was just the day before the actual exhibit that we got the relay to open when the probes were touched together.
Posted on 2003-05-05 22:56:44 by AmkG