A while ago now Glyn and I worked on a design for a 12 input pulse counter, we where doing some work at the Centre for Alternative technology, a stripboard version was built and is in continued use monitoring grid import/export, chp and diesel generator (the last two not actually in active use).
We wrote up about it here:
After visiting CAT again recently and discussing a project they hope to do, it got me thinking again about the 12 input pulse counter. In non-domestic buildings that already have pulse output meters on many of the circuits and a meter room with all the meters in one place, a multiple input pulse counter may be the most effective way to add automatic meter reading.
I've wanted to make a PCB for the 12 input pulse counter for a while so I though I'd do a little work on it this morning, here's a screenshot of where I've got to so far:
Here are the features Im thinking it will have:
- 12-input pulse counter
- Optional pull down resistor with option for SMT or through hole, see building blocks pages linked above for why pull down resistors are required.
- Input status LED, driven by pulse signal.
- Dedicated ATmega for pulse counting
- Serial connection to second ATmega used for ethernet or/and rfm12 comms.
- Enclosed in a DIN rail mounted enclosure.
Here's the eagle design so far:
I used the rfm12pi board design as a starting point as it already had the basic atmega + rfm12 circuit in place.
One thing I'm still wondering about is whether to add a second optional resistor between the terminals and the pull down resistor which would provide the option of having a voltage divider on the input for stepping down from higher pulse voltages like 24V.
More to come soon..