EEV Testing

[SkyWalker]

Hi guys, I was wondering how you guys go about testing EEV if you suspect them as faulty?

they all seem operating with a "step" motor, i know very little about this and cant seem to find anything? when ever i ask anyone they just say "it cant be checked as its a step motor" ?? i fail to accept this?

there are obviously a few things that could wrong, said step motor may be faulty, it may be mechanically broken, blocked, or the PCB isnt giving it the correct supply?

a dead test, Ohming out the motor is simple enough but what sort of supply from the pcb should these things be getting?

If i suspect a faulty EEV the things i check are for a "clicking" on power reset, systems do this to ensure valve in correct postion, check temp diffs over EEV and Ohm out coil.

but if i cant check PCB supply how can i be sure its a mechanical fault or a PCB fault?

Could you guys give me any other info or advice on tecting EEV's?

thanks guys, hope you follow :rolleyes:

[Brian_UK]

There are some fault finding details in this Sporlan document...
http://www.sporlanonline.com/SD-348.htm

and... if you wonder what the SMA is that is mentioned in the above, read here..
http://www.sporlanonline.com/SD-213.pdf

[SkyWalker]

thanks brian i will have a read.

[james10]

Most EEV'S have a predtermined resisitance the best way i have found is to get hold of manufacturers info and go by that if you have a specific model thats giving you trouble give us the model and maybe can help you more

[SkyWalker]

Ok James thanks, I was more in "general" terms, I don't have a fault to fix at the mo.

[Peter_1]

they all seem operating with a "step" motor, i know very little about this and cant seem to find anything? when ever i ask anyone they just say "it cant be checked as its a step motor" ?? i fail to accept this?

This isn't quite right: many of those works via the PWM principle

[Peter_1]

Some brands like Daikin have permanent magnets to turn open manually their EEV's. You then can find if the EEV is mechanically faulty or the PCB

[Peter_1]

a dead test, Ohming out the motor is simple enough but what sort of supply from
Ohming and meggering the resistances tells you if the stepper motor is faulty.
Most windings in the stepper motors receives a block voltage, a short pulse, in a certain sequence. You only can see this with a scope. It goes that fast that you can't measure this with a digital meter.
You also have unipolar and bipolar switched systems.
The only thing that you can do is switch a LED with a voltage-drop resistance on the wires to the motor, something similar to the cheap inverter controllers.