using a 360 degree servo as a temp gauge

[ArduinoM]

Like i said NOT A GOOD EXAMPLE, but finding a cheap one that takes -+ 5V should not be too hard, just to mod and hack with, I have seen meters with alterd background, and with arduino to control the meter it is easy to mark up a new background by outputing standard control series of signals eg. 1v 2v 3v...

[tobycatlin]

like i say expensive and ugly. If i can't build my own for cheap then i was planning on buying a off the shelf electronic gauge and changing the face

if i can rig up a home sensor then this looks like it might work.
http://www.blog2.angryviking.com/?p=49

code
http://www.blog2.angryviking.com/?p=58

Not sure if my 360 degree servo will work instead of the stepper motor.

[ArduinoM]

360 servos are used in CNC and then with rotary-encoders, it should work, but precission is not guarantied if the rotary-encoder only travels about 360 deg. for so small travel to work the rotary encoder should give you 256 or 512 or 1024 signals for full travel of the needle and an indication of start point and end point (the meter should be calibrated on startup). Good luck.

D.

[george_graves]

A stepper motor is your best bet:
http://www.blog2.angryviking.com/?p=49

[ArduinoM]

Oh.. forgot..
You could salvage a small stepper from a broken printer or scanner.
that is the easiest way. Electronics stores are required to take broken el-equipment back, and often store them behind of the shop in containers
Relatives and friends probably have an ancient printer in the attic, those are the strongest ones because printers and scanners in the old times were heavy and bulky.

D.

[tobycatlin]

"for so small travel to work the rotary encoder should give you 256 or 512 or 1024 signals for full travel of the needle"

can you elaborate? If i understand it correctly i would have to add a rotary encoder to the servo to provide feedback. sorry if this is a obvious question, i just want to make sure

[ArduinoM]

Ah.. sorry I  assumed hommade rotary encoder, with optic sensor and black and white pixels (perhaps on the backside of the dial).

But of course you can buy rotary encoders that do the job for you,
you could try sparkfun.com, but I think theres are not suiteble and threre is digikey.com and all the robotics shops.

And Yes the rotary-encoder is for feedback, it counts the steps the needle travels on the dial, could be timed so you have x ms between black or white (or just counts the time between signals if you would) and you stop the needle say 156 ms after signal nr. 66... and so on...

Google rotary encoders, often there are patterns for "total" knowledge of where on the circle one is.

Still easyest is the salvaging of a scanner/printer stepper.

D.

[tobycatlin]

just having a poke around a old 3.5" floppy drive. i keep it about for emergencies but havn't used in years.

it has a small stepper driving a worm gear to move the head. it has four wires coming from it, red white black and brown. Is it worth destroying the drive for. I do have a printer but it is a working inkjet so can't butcher that.

might have to have a scavenge at work, internal systems must have a old tape drive somewhere

[ArduinoM]

If you have an Hall-efftect sensors with a magnet, you could use them for feedback for the servo. Maybe 3 hall-effect sensors and triangulating

[Maico]

tobycatlin, cool project with that gauge clock

[zoomkat]

There is a winch servo that has ~720 deg of rotation. For something light weight and simple like a dial needle, a simple mechanical up gearing setup can be made to work with a standard servo.