Pretzel LogixWhile designing a project that required 5v USB power ports from a much higher voltage source (eg. 12v or 24v), it occurred to me that there are circuits already designed to do this. In fact, not only do they exist as low-cost, easy-to-purchase modules, but some of them already have the USB port soldered onto the board.
Four Step-down converters with USB ports were picked out and reviewed in an attempt to find “the best cheap USB switch-mode step-down converter” for 12v power supplies.
With the current DIY/Maker movement in full swing, one thing that almost all of us need is a good Multi-meter. When shopping for one, it was decided right away that a good entry-level multimeter for beginners had to be:
Digital for high precision, Auto-ranging to eliminate the need to switch the dial every time something changed, and $50 maximum to keep this within the budget of most DIY’ers/Makers like you and me. (As an aside, the requirement for an Auto-ranging feature also makes the minimum around $20.)
After perusing Amazon, it was discovered that 8 models fit this criteria. The biggest problem was that all 8 of them reviewed really well typically averaging between 4.4 and 4.7 stars.
The customer reviews were okay for getting a feel of each model, but they were so inconsistent that there was no way to compare and contrast one model with the next. So one of each was purchased and immediately we began the going over of the models while poking and prodding each one.
A few weeks back, Redditor /u/doakey posted an insanely cool idea to /r/arduino of lighting up his toilet bowl with a red laser so that when he got up in the middle of the night to pee, he could see where he was “shooting”, so to speak. And it was a grand success!
Walk into the bathroom. Laser shoots into the bowl. *pew, pew, pew* Lights up the target like a spotter for some stealth aircraft to hit with a smart bomb. Night vision preserved. Mission accomplished. Laser turns off. Then you go back to bed.
Yet, he noted that the 9v battery only lasted a few days. Naturally, a few of us pointed out that an Arduino is overkill and that he could have done this using analog electronics.
And I get it. Analog is pretty hard. Arduino is relatively easy. There are plenty of resources out there on how to program Arduinos, but analog… well, it is kind of on its way to becoming a “lost art”.
A few people in /r/arduino asked me to write-up my proposed analog verson. After a few weeks of fiddling, here’s the analog circuit (and explanation) I came up with to reproduce the same effects…