RPM

Started by meriachee January 25, 2010
Hi gang,

I just got a mini lathe, and am thinking about making a nice little tachometer for it. I know there's a whole pile of new stuff at Solarbotics, but I haven't researched anything yet.

If anybody has done something along these lines, what did you use for a sensor?

Cheers
Gary

Hi Gary,
I have built tachometers for my lathe, mill and drill press.
I used a variable reluctance transducer on my lathe a hall effect sensor on my mill and a reflective opto on my drill. I would not recommend the variable reluctance type as it is quite bulky, does not work well at very low speeds and needs more playing round with the signal conditioning. The hall effect device I used on the mill is a type that requires a separate magnet. The device I used (I can not remember the part number but I could find out if you wanted me to.) looked like a small surface mount transistor. I mounted this on the end of a length of 0.25" paxolin rod with a very small magnet behind it. This works very well but takes time to make the mounting for the device and magnet. I have now found a hall effect gear tooth sensor which has the magnet built into it (Allegro ATS642LSH) I have not put this onto a machine yet but it works very well testing it on the bench by holding it close to the teeth on the chuck of an electric drill. This sensor is a two wire device so needs a current sense resistor and a comparator. There is a three wire device in the device family but I can not find a supplier here in the UK. I think this could be connected directly to the PIC. On the lathe and mill I count pulses from an existing gear on the machine. On the drill I have stuck a reflective marker on a pulley. I have designed a tacho using a PIC16F628A. This can be used with any number of pulses from 1 to 99 per revolution. If you are interested I will but the design in the file section of this forum.
Les.

--- In p..., "meriachee" wrote:
>
> Hi gang,
>
> I just got a mini lathe, and am thinking about making a nice little tachometer for it. I know there's a whole pile of new stuff at Solarbotics, but I haven't researched anything yet.
>
> If anybody has done something along these lines, what did you use for a sensor?
>
> Cheers
> Gary
>