Here is the current meter hack …
Nice where did you get it?
That’s exactly what I want to do, after the numerous other things that I want to do. Great hack.
@donkjr I was wondering why the reading only went to 4.9 at max. Makes sense now. It’s the voltage.
I have a couple dozen of these little volmeters, in various colours. Think I will add it in to my K40 and Redsail LE400
Yup @Yuusuf_Sallahuddin_Y its a relative measure of power but its just reading the voltage off the pots center wiper which is what is controlling the laser supply?
From what I recall, the current meter is typically connected to ground on the return line from the laser. So theoretically if you put one of these voltmeters in
parallel with a 1k resistor then your voltmeter could replace the existing ammeter and read the current in mA.
I would assume you can just put a digital ammeter where the analog meter is. The current version of these meters have an internal shunt. I did not like a digital circuit in a HV ground …
But the problem we are solving is that the current meter doesn’t show anything until the laser fires. The pot controls the HV PS by applying a 0-5v value whereas the voltmeter shows you it relative position all the time.
Stop doing these cool things so I feel the need to yet again mod my machine!!! lol
@donkjr ah, that’s cool. Perhaps then a meter like this that claims to be “adjustable” could let you rescale the number displayed up enough to display either a milliamp value or a percentage? http://www.amazon.com/gp/product/B0154KFZFU
@Vince_Lee1 if by adjustable they mean that you can change the scale that would work. They don’t explain adjustable though. I suspect it is the same as this one https://www.adafruit.com/products/705
which is not what you want. This type of meter isolates the display voltage from the measured voltage and that is why there is three wires. It is not scale adjustable.
Certainly you could put a circuit between the pots center wiper that would scale the display on a voltmeter. You could do it with a op amp or get really fancy and put an arduino in between. I originally was going to do that but I decided to use this until I just upgraded to a new DSP as there were so many other uglies that needed to be fixed. Turns out for me whether I set it 0-4 for power or had a nice 0-100% they are both relative anyway.
The right way is for the DSP to control the power anyway.
@donkjr Yeah it wouldn’t be too problematic to convert 0-4 to a 0-100 in your head. As you said, it’s all relative anyway. I like the way that it is always telling you the value, not just when you fire the laser. +1 that.
@donkjr ok. I guess you can always make a voltage divider with two resistors to scale down the number to say from 0 to 1.0
@Vince_Lee1 you can make a voltage divider but you have to isolate it from the input to the power supply as the pots wiper is controlling the laser power supply (our meter is just measuring that). That’s the reason for the op amp in between the pot and the display:)
FYI here is how Light object puts a digital meter ammeter in series with the tube
http://www.lightobject.info/viewtopic.php?f=16&t=1759
@donkjr A similar meter I looked up says it has a 100k internal resistance so can’t you just add say around 400k resistor in series it would divide down the measured voltage.
Why not just use a double pot, take any reference voltage you can get from anywhere in the machine (say 5V DC), add a tr54immer to calibrate it to whatever you like?
Sorry for the silly question, is this wired in between center lug of the pot and ground?
Looking from the back of the panel and back of pot and the solder lugs are downward facing. Connect as follows. I pulled off existing lugs soldered these on and then pushed lugs back on.
Meter black on left
Meter white in middle
Meter black on right
I will post a picture …