Thursday, 8 December 2016

The making of the pulse stretcher

This is a follow up post about the pulse stretcher I made for my CNC, which you can read the details about here:

I made a video about it as well. The reason is that I am really happy with the results, the LEDs are flashing like crazy at the right pace, easy to see from any angle, unlike before, and if I wanted to see the status I had to be in front of them to see anything. The intensity is simply too low at high speed, so stretching is necessary.

The circuit is really simple, just a few resistors and capacitors and two 74HC14 inverters.

Anybody interested can just make the same circuit. If you are not happy with the pulse lengths you can play with the four resistors (R1, R2, R3, R4) and/or the four capacitors (C1, C2, C3, C4) to change the behavior of the circuit. I used Eagle to draw the circuit and to create the layout.

The PCB turned out really nice, no additional work needed with cleaning the tracks or anything at all. Traces are beautifully milled and follow what's been routed with the auto router of Eagle. Manually routing or double sided PCB would have created a more beautiful art work, but it is good enough.

I hope you enjoy the video, it shows not only the work flow, but also a before and after sequence.


I just noticed an error in the video. I mill the first pass at 0.04mm depth and the second pass at 0.07mm and nothing else. In the video I wrote that I mill the first pass at 0.4mm and the second at 0.7 and that is just too much for PCB milling. The copper layer is just 0.035mm, so there is no need to mill deeper but I double that value to be on the safe side, however, making it 20 times deeper than necessary would be crazy.

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