Cheap Multimeter Gauges Embedded Idle Time

How often is your microcontroller actually doing something? You can find out by measuring idle time, but how exactly do you do this? [Jack Ganssle] shows that simple embedded applications can toggle a pin when idle, which can then be measured. More complex applications like those using a Real Time Operation System can do the same by making use of the idle hook. But what can you do to make this toggling pin feedback actually mean something?

His solution is to repurpose an analog multimeter. The meter is interface with the toggle pin and a trimpot calibrates the needle. This way the needle jumps when the processor is busy and returns to zero when idle. What a great tip for getting a little more feedback about what’s going on inside of that black plastic IC package. It’s not surprising to find such a clever hack from one of the Hackaday Prize judges.

While you’re in the analog multimeter aisle you might want to pick up a couple of extras for more alternate data displays.

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Digital Caliper Sacrificed For DRO Project

In general, machining metal on a lathe or mill takes skill and patience as the accuracy of the cuts are important. To make those accurate cuts, it is important to know where the tool is located and how far it moves. For manual machines, the most basic method of determining position is by using graduated dials mounted on the hand cranks. Although these graduated dials can certainly be accurate, they may be difficult to see and they also require the operator to do math in their head on the fly with every full revolution of the dial. Another option would be a digital read out (DRO) which has an encoder mounted to the moving axes of the machine. This setup displays the exact position of the tool on an easy to read numeric display.

Professional DRO kits for mills and lathes can cost between a few hundred dollars to several thousand dollars.  [Robert] has a lathe, wanted a DRO but didn’t want to shell out serious cash to get it. He built his own for super cheap in an extremely resourceful way…. using a Harbor Freight Digital Caliper. A housing was first fabricated so that the added equipment would not hinder the axis travel of the lathe. The caliper was then cut to length, installed in the housing and the entire assembly was then mounted to the lathe.

DIY Lathe DROIt is totally reasonable to use the stock caliper display to read the positional information, however, even these cheap digital calipers have connections for the encoder output data, which can easily be read by a microcontroller. That means it is super simple to hook these low-cost digital calipers up to a display remotely located in a more convenient position.