Introduction

The Beeper box is a fabulous bit of kit designed and built by Pauline Loader in NZ. This has been a very cost effective way of getting millisecond timings for occultation observations (More detail here). Most recently, Hristo Pavlov has written a software utility Beeper Sync to allow the time to be set from any PC connected to the Internet.

Unfortunately, the Beeper Box was designed in the days when parallel ports were the norm and this is very much no longer the case.

My nephew David, on holiday from the UK and I were pondering life the universe and everything in my observatory whist waiting for nothing to happen with regards to an asteroidal event. I was showing him the Beeper Box and bemoaning the fact that I had to maintain and ancient PC just to make it work. He happened to mention that as part of his first degree (for he has many!), he studied electronics and in particular interfacing, and that it was not difficult to convert the device to serial.

He wasn't wrong! So many thanks to him and thanks to Hristo for modifying Beeper Sync to accommodate it. This is what we ended up with (cover off):

How it works

In essence the Beeper Box sets it's time based on a momentary voltage drop from +5v to 0 then back again.

This is not however how serial interfaces work. From Wikipedia: "The RS-232 (Serial) standard defines the voltage levels that correspond to logical one and logical zero levels for the data transmission and the control signal lines. Valid signals are plus or minus 3 to 15 volts - the range near zero volts is not a valid RS-232 level."

To make this work therefore, we had to ensure that only a positive voltage was received and that any excess voltage was scrubbed off. Then all we need to do is simply use connect and disconnect commands to operate the device.

Enter two very cheap electronic components:
1. A diode - This is in effect a switch. It will only current in one direction, and gets rid of any -ve voltage.
2. A voltage regulator - this simply burns any exesss voltage in heat, and outputsits specified voltage (or lower)

Wire up these parts and you have in effect recreated the signal from a parallel port. Simple as.

Building one

I am rubbish with a soldering iron so if I can do it, any one can. If you really don't feel up to it, ask a mate. If there is enough interest I may put together a parts kit...

You will need these things:

And this is how they connect:

Disclaimer

It's not my fault if you stuff something up! Please test the output of your device with a multimeter before using it - that voltage should not read more that +5, although it may be less if you have a low voltage serial port.

The design is cheap and cheerful and should be considered as such.

Have Fun!

Jonathan.

Credits

Jonathan Bradshaw - The problem (and red wine).
David James Bradshaw - The solution.
Hristo Pavlov - The software to make it all work.