Interfacing a 24 volt signal to parallel port

[macona]

I am trying to interface my sensor I am using to provide spindle feedback. It is a keyence fiber optic sensor and it outputs a 24v pulse. I had planned on interfacing it with a opto22 dc input module but it does not seem to like frequencies above about 100hz. Any signal above there seems to disappear.

What are my options. The output of the sensor is limited to 40 ma. The interface board i have for my parallel port uses SN74ACT245N buffers. Maybe an optoisolator? What about using a couple resistors for voltage divider?

[Servo Wizard]

macona,

The IDC5 module that you have has a 5ms on time and 5ms off time, or a 10ms cycle time. (1000/10=100) Opto 22 G4IDC5K has a .025ms on and .025ms off time, or a .05 cycle time. (1000/.05=20000)

Servo

[CNCezee]

I would not use an opto isolator due to there being a turn on and turn off time which limits the speed of opperation,
I would use a pnp transistor (BC212 type) using the +24 signal potted down to turn off the transistor ( signal low transistor on )with the emitter voltage supply at +5 volts, then if required use a standard gate to shape the output signal.
However to do this the +24 volt signal ground and +5 volt ground must be common

Roger

CNCEzee

[Al_The_Man]

What is the nature of the output signal from the fibre optic? you may not need to isolate it. If not either feed direct to the 74245 or buffer it with a 2N7000, make the common of the optic sensor common to the 74245 common.
I just noticed you mentioned the 24v optic signal, you could still use the 2n7000 with a voltage divider to the Gate.
Al.

[The Speaker Guy]

There's a few ways to do this

A voltage dvivder into a a 74HC14 Schmitt trigger. Simple, easy to get part. Use a 20k resistor on top, a 3.9k resistor on the bottom. Question is if the signal source can drive the R load well.

Use an LM339 comparator. You get four per package, and these operate up to 36V. Set IN- to 1/2 of the peak operating voltage. Connect the IN+ directly to the signal source. Advantages are no load to drive from signal source, and this circuit works from 5V to 36V with no changes.

http://www.national.com/pf/LM/LM339.html

Good Luck

John

[ViperTX]

I personally like SpeakerGuy's approach...voltage divider and feed that into the 74HC14.....it will also provide you with some debounce if necessary.

[ger21]

http://www.cncbuildingblocks.com/ele...interface.html

[pminmo]

Need to know more informaion. Looking at the keyance website, several different output configurations. Do you have a model number? My fear is they have slow rise and fall times. If that is true a comparitor configured with a lot of hysterysis, and large signal swing would be best.

[macona]

The module is a keyence FS-V1P with PNP output. The module I am using is the Opto22 G4IDC5D.

I put the scope on the output and found it has a good turn-off response time but by the time it gets to zero the next pulse starts. I tried loading down the output with a 200 ohm resistor and it cleaned up the waveform a lot. I have a pretty clean signal up to about 1200 RPM with a 4 mark encoder wheel (4 black, 4 white) and from there I start loosing it again. I dont think its the opto22 module but the signal quality.

I think I will try the schmitt trigger and see what that does.

[Al_The_Man]

What about a MC1489, this is a very common data reciever ic but it takes up to +30v input, will condition the signal and has a response input pin that can tailor the trigger point, outputs to TTL.
Al.

[macona]

I got it working. Combination of two things. First was the resistor across the output of the sensor. This cleans up the fall time nicely. Second was switching the input to the second parallel port board (I am using two parallel ports on this machine) After looking at the output of the opto22 module I found I was getting a good signal out of it after all. I checked the output to one side of the 74245 and it was pretty good. I went to the computer side and it looked like crap. In the chip it looks like it was picking up interference. My best guess it was from the spindle drive.

So it all works good now. Set up closed loop spindle control and got it tuned pretty well. I can run it dead slow, put my hand on the spindle to stop it and it kicks up the power to compensate within a second or so. I think it would do it faster after I play around with the decel parameters in the VFD.

Yay! Thanks Guys

I cant wait to upgrade to the G100... Bye Bye parallel ports...

[shaheen]

i try to do the same project and i face the same problem