555 as an encoder?

[Rather Play Pinball]

Have a device with a corded remote control. 3 conductors. Had to take it
apart. Inside, the conductors are labeled +V, Gnd, Signal. The remote is a
6 button job. There's a 555 and a transistor nearby. Lots of resistors
and caps.

So? Any guesses what they send out? A square wave with the number of
pulses to correspond with the button number? A single long pulse with the
width in proportion to the button number?

How would you design it?

 

[Tim Wescott]

Rather Play Pinball wrote:

Have a device with a corded remote control. 3 conductors. Had to take it
apart. Inside, the conductors are labeled +V, Gnd, Signal. The remote is a
6 button job. There's a 555 and a transistor nearby. Lots of resistors
and caps.

So? Any guesses what they send out? A square wave with the number of
pulses to correspond with the button number? A single long pulse with the
width in proportion to the button number?

How would you design it?



You could do one pulse with 6 different widths, you could encode rows

and columns as on and off times, you could do something wilder.

I think that having the number of pulses vary with the button is the
least likely.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

[Terry Pinnell]

"Rather Play Pinball" <123@123.net> wrote:

Have a device with a corded remote control. 3 conductors. Had to take it
apart. Inside, the conductors are labeled +V, Gnd, Signal. The remote is a
6 button job. There's a 555 and a transistor nearby. Lots of resistors
and caps.

So? Any guesses what they send out? A square wave with the number of
pulses to correspond with the button number? A single long pulse with the
width in proportion to the button number?

How would you design it?


What's it controlling? If it's a servo motor, then the 555 is probably

sending control pulses of around 50 Hz with pulse widths between 1-2
ms, to position the motor.

--
Terry Pinnell
Hobbyist, West Sussex, UK

 

[Anthony C Smith]

"Rather Play Pinball" <123@123.net> wrote in message
news:1vALd.3741$_X6.2606@fe07.lga...

Have a device with a corded remote control. 3 conductors. Had to take it
apart. Inside, the conductors are labeled +V, Gnd, Signal. The remote is
a
6 button job. There's a 555 and a transistor nearby. Lots of resistors
and caps.

So? Any guesses what they send out? A square wave with the number of
pulses to correspond with the button number? A single long pulse with
the
width in proportion to the button number?

How would you design it?
Most simple form of remote, by changing the timing resistor the 555 gives a

different frequency for different buttons pressed, or varying the control
voltage pin (pin 5) which will change the trip point for the turn off
(discharge phase)
frequency would be the easiest to decode with either a micro or tone decoder
(such as lm567)- I am amazed they require all three wires- I've done this
trick with 2 wires, ground and a combined power/signal by superimposing the
square wave frequency onto the power line.
Another trick to lower the emc problems is to charge the cap on the 555 with
a current source (maybe the tranny on the pcb) and then use the VC (pin5) to
vary the frequency of the resulting triangular wave on pin 6
Smashing chip the 555
Regards
Anthony

 

[Rich Grise]

On Mon, 31 Jan 2005 19:54:58 -0500, Rather Play Pinball wrote:

Have a device with a corded remote control. 3 conductors. Had to take it
apart. Inside, the conductors are labeled +V, Gnd, Signal. The remote is a
6 button job. There's a 555 and a transistor nearby. Lots of resistors
and caps.

So? Any guesses what they send out? A square wave with the number of
pulses to correspond with the button number? A single long pulse with the
width in proportion to the button number?

How would you design it?

You've got it this far apart, and haven't traced the circuit yet?

Do that, and tell us what you find, and the answers will be much easier to
understand.

And they'll be a lot more likely to have anything to do with what you have
in your hand.

Good Luck!
Rich