Building a probe

[hughesbros]

Originally Posted by itsme

Is an amplifier really necessary, or can I simply run 5V through the probe directly to the parallel port? I would obviously like to make it as simple as possible, but if an amplifier is needed, then I'll have to make one.

The MaxNC probe works on 5V, I found it was not very sensitive and you would get spikes in the scan. From what I can remember the printer port does not work 5V on 0V off its something like above 2.75V is considered on and below is off so there's not a big differential. Any bad connection at the lower voltage and the control thinks it is in contact and lifts until the resistance drops and you get a bad reading. Using 12/14v with the amplifier gets over most of the problems with resistance in the switches.

When I get a chance I'll post a picture of the amplifier I built and a drawing of the PCB board. I made the PCB board on a mill so it's quite easy to make if you can get the components.

Mark
Hughes Tooling.

[itsme]

Hi Mark,

Thanks for the information. If (when) I'm going to make the probe, I may as well do it all properly. If you could post pictures of your PCB, that'd be great. The other photos you posted are also awesome. I'm inspired to build a probe!!!

Regards
Warren

[PEU]

I found this Renishaw page that show the innards of their probe:Link

Pablo

[itsme]

Thanks for the link, Pablo. Isn't it strange how the Renishaw innards look so similar to the probes that people build at home???

I've been looking at the amplifier schematic and I've been having a few thoughts on how I can adjust it to suit my requirements. With my CNC setup, I'll have a 35VDC supply. It would be nice if I could put the probe electronics inside my CNC control box and then use my CNC machine power supply. Would the probe be able to handle 35V? I doubt anyone has tried it, but what do you think???

I also have a few questions relating to the actual amplifier running at 35V, but I felt that these would be better placed in the 'General Electronics Discussion', so I am going to start a new thread there (just in case anyone is interested...).

Regards
Warren

[PEU]

well the probe is a simple on-off switch, if the current is not very high I see no problems. the problem is how do you feed 35v back to the parallel port

IMHO is easier to use a proper voltage power supply, switching cellphone chargers are a very cheap source of power supplies, they usually have a pot inside that sets the output from 4 to 12v


Pablo

[itsme]

Hi Pablo,

If you have a look back in one of the earlier posts in this thread (from hughesbros), you'll see the plans for a probe and also the amplifier that goes with it. The probe in those plans normally operates off 12V, which is also too high for a parallel port - that's the purpose of all the circuitry. All I want to do is modify that circuit to run off 35V instead of 12V. Why do something the simple way, when you don't have to...

Regards
Warren

[Al_The_Man]

I don't see why you need extra supplies when you have them in the PC if that is what you are using?
Al.

[Zathras]

What about using a piezo as the transducer?
STMs use a piezo tube to move the probe across the suface.
See this homebuilt version;
http://www.e-basteln.de/

renishaw has piezo probes;
http://www.renishaw.com/client/produ...PGP-1070.shtml

Or maybe look at an AFM;

http://www.nano.geo.uni-muenchen.de/...3_document.htm