Tuesday, 28 August 2012

10 Turn Counting Dial

Laser cutters have dropped in price and are now well within the hobbyist price bracket. These low end lasers tend to come without some of the features you find on more expensive machines and perhaps one of the worst cost cutting measures is the 10 turn dial to control laser power. The standard dial has no indication to let you know what power the laser is set to, meaning you have to turn it all the way back to zero and then count the number of rotations just to be sure but there is a simple after market modification that I would recommend you do as soon as you get your laser home. Farnell part no: 1219790 is a 10 turn rotary counting dial that will save you endless hours of faff. It can be mounted on the output of the existing potentiometer and it counts the numbers of rotations from a zero point.

The item arrives bagged with a set of instructions and a small Allen key used to fix the dial to the shaft. This version of the dial features a locking break and a window over the digits. Priced at £21.19 it's the cheapest dial I've found where the numbers all line up in a row along the top of the dial, giving a simple readout of the current value.

The knob is removed with a straight pull and it is keyed to prevent it being put back in the wrong orientation. This exposes the two fixing grub screws in the shaft perpendicular to each other. The dial shaft is open at both ends, once placed onto the 10 turn pot you can still use a screwdriver onto the end of the shaft to ensure it is in the zero position. Set the dial to zero, rotate the shaft to the zero position and then tighten up the grub screws, it's (almost) as simple as that. The underside of the dial has an alignment pin to keep the dial vertically aligned. A hole can be drilled through the laser case to locate with this pin or the pin can be cut off. I took the later option as I wasn't sure about voiding my laser warranty, I then used some strong tape to keep the dial vertical.

I mentioned that it was almost as simple as putting it on the shaft to install it. The only minor inconvenience is that it's the wrong shaft size. I've been unable to find such a dial to fit a 4mm shaft but when you have a laser every problem has a laser cuttable solution. I created a small 'shim' to increase the shaft size of the pot and make it fit the dial, the grub screws squeeze it tightly and hold it against the pot shaft. (svg here)

This is a great little dial that will save you hours of time on your new laser cutter. Once mounted to the control panel it looks like it was always there and it makes a satisfying little clack as the numbers spin round. It is irritating having to spend more money straight after buying an expensive laser cutter but this is a very worthwhile investment. http://uk.farnell.com/vishay-spectrol/15a31b10/counting-dial-digital-10-turn/dp/1219780

Also don't forget to make a big height adjustment wheel as one of your early mods