using a 360 degree servo as a temp gauge

ah well they do say assumption is the mother of all screw ups. I assumed because the description said it was a servo it would act like a servo. So what i have is more of a stepper motor, right?

to get this to work as desired i would need to feed back the position of the needle, right? Could I do this with a encoder wheel? http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1257038219

I am tempted to get a standard servo for an easy life but i really want a range of motion more than 180. A standard servo that operates between 0-360deg would be ideal.

any ideas?

these might do the job: http://www.pololu.com/catalog/product/1218

I have a feeling there must be something better for the job. Would i be better off with a stepper motor

LCD Panel and have a nice digital temperature gauge and make it do speed, tachometer and oil pressure as well ? :)

I have done some gauges using processing and could display them on a lcd screen from a cheap netbook. I want to see some needle leaping about and i want to make use of some funky led's.

I can buy commercial servo driven gauges but most of them are expensive and ugly. I was hoping i could make one cheaper and prettier. Plus it's more of a challenging problem.

I think i have found the products i want but dont know where to buy them

Freescale MCZ33970 http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=MC33970

Series 6405-15xx Stepper Motors http://www.fraenamd.com/steppermotor.htm

anyone know where to get these products in the uk?

I want to see some needle leaping about

On a temperature gauge ? , the one on my car goes to 90 C and doesn't move again. Very boring.....

well yes, a temp gauge isn't going to jump about. I want to make a set of dials for a dash board. The principle is the same.

Maybe i should have titled this "i want to drive a gauge from and ardiuno" I should have done more research before buying the 360 servo, but it also seems a standard servo won't do what i want anyway.

I am learning plenty

Vacuum gauges are fun for leaping needles, but my latest car is a diesel and they don't have a vacuum to measure. Also very boring :(

If you could rig up a rack and pinion arrangement with the needle on the pinion and have the servo push and pull the rack, the servo wouldn't need to move very far. Just an idea.

Why not just use standard car gauges that are controlled electrically 0-5v or +-12V and controll them from arduino? like: http://www.egauges.com/vdo_grou.asp?Series=DBF_Amber (not good example but these go more than 180 deg)

It is maybe possible to take those meters apart and change the background of the needle to suit your needs 8-)

D.

200 bucks a throw ? Ouch......

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...

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.

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.

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

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.

“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

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.

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

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 :)

tobycatlin, cool project with that gauge clock :)

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.