I like perfboard, especially the ones with plated trough holes. But I also like SMD components, and more and more fun IC’s are not available in DIP. So a while ago I designed some perfboard with 1.27mm pitch, making some SMD parts like SOIC stuff easy to prototype on it, and also mix THT and SMD stuff.
Looking for a nice little project to build on it, I came across a frequency counter made with 7400 logic, perhaps not the most efficient approach, but a fun one at that. I made a few changed to the design, partly because of some components I already had like the 74HC160 and 4543 (yes, not 7400 but still logic :P) and partly to improve on the design, for example by adding a 10Mhz oscillator instead of a NE555 as the clock source. The current end result looks like this, a case is ordered and a follow up post will be made when the project is nicely tucked away in a case.
Dan Watson documented on his blog an OCXO upgrade board he designed for the Fluke/Philips PM66xx line of frequency counters:
My counter came with the standard XO timebase option, which has fairly poor specs for stability and drift. It is difficult to trim precisely with the single-turn trimmer capacitor on the board. For most testing in my lab I use an external reference from a GPSDO, but it is still nice to have an accurate timebase available in the counter if I need to take it somewhere and do testing away from the bench.
Previously I posted about an OCXO upgrade I made for my Racal-Dana 1992. The fun of designing a similar upgrade for the Philips counter was one of my motivations for purchasing it. My upgrade board is roughly equivalent to the original PM9691 OCXO module, and it should be compatible with any Fluke/Philips counter that is capable of using that option.
Andy Brown has designed and built a frequency counter using an FPGA, STM32F072 and an Android GUI – the Nanocounter:
After studying the above counting methods I decided on the following goals for my frequency counter, which I’m going to call Nanocounter.
Very accurate measurement over a range of 1 to 50MHz. This would cover the range of MCU crystals that I’d want to measure.
Onboard accurate, but cost effective reference with the option to feed in an external reference clock source.
Advanced options including data logging, charting and calibration of the onboard reference.
That should do for starters, let’s see how I get on. This project will call upon a large number of engineering disciplines including circuit design, PCB layout, SMD reflow, FPGA design, C++ programming and java android programming so I should be in for a fun time.
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