From: Ben Harris Date: Thu, 22 Nov 2018 00:06:01 +0000 (+0000) Subject: Minimal documentation for ClunkPi. X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~bjharris/git?a=commitdiff_plain;h=a1a776289cd4f3a5c89f9e6e6aff8d16022ae22d;p=clunkpi.git Minimal documentation for ClunkPi. --- diff --git a/index.xhtml b/index.xhtml new file mode 100644 index 0000000..abfe4f0 --- /dev/null +++ b/index.xhtml @@ -0,0 +1,43 @@ + + + ClunkPi: driving pulse clocks with a Raspberry Pi + + +

ClunkPi

ClunkPi is an add-on board to interface a Raspberry Pi to a + pulse clock. It is designed to fit all models of Raspberry Pi, + from the Model A onwards. It can operate any clock that's + compatible with the British Post Office class A system, + including movements made by Gents, Synchronome, and English + Clock Systems. ClunkPi can be driven by the + Clunk + software to provide an NTP synchronised pulse clock.

Specifications

ClunkPi fits the 26-pin I/O header on the original Raspberry + Pi. It should also work on the first 26 pins of the 40-bit + header used from the Model B+ onwards. The board is smaller + than either a HAT or a uHAT, so it should fit many cases.

ClunkPi is essentially a switchable current source. It + provides a current of 250 mA Â±10% into a resistance of up + to 12 Î©. It is switched by GPIO line 17 from the Pi. It + is powered by the Pi's 5 V line, from which it needs + 250 mA.

In theory, it should be possible to run ClunkPi off a higher + voltage to drive multiple clocks, up to the 50 V limit of + the drive transistor.

Design files

I designed ClunkPi using + KiCad. The KiCad source + files, along with the Gerber files for PCB manufacture, are + available for download.

Circuit description

The circuit is a simple current source controlled by a shunt + voltage regulator. U1 and R2 control the base current in Q1 to + achieve 1.24 V across R1. D1 suppresses any voltage spike + caused by the inductance of the clock coil.

Use

Plug the board into a Raspberry Pi with the square solder pad + connected to pin 1 of the GPIO connector. Connect the clock + (either way around) to the pads labelled "J2".

+ +