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Paul K.
07-28-2005, 08:24 AM
Hello all,

Well here is alittle background info on my project.· I work at a distrubution center that sends totes around the building and there is a tote cleaner that turns the totes upside to let trash fall out.· We now want to let a burst of air jar loose anything stuck while the tote is upside down.· I have alot of these Rockwell Automation Series 7000 Photoswitches which are used for high speed merges, diverts, and motor control.

I have built the two solenoid circuits using a irf 520 and they work great.··To try them out·I simply use a high/low command to enable and disable them just delaying the pause to let more or less air thru.·

Now I need to control when they go off and·I plan to·use this sensor http://www.ab.com/catalogs/sensors/catalognumberpdf/ch1/1-180_1-189.pdf.
I·am using the NPN on page 1-188·visible red light.· I have hooked the two up to a 24v 5@ power supply and i checked what the green(NO) and white(nc) wires output when the beam is broken and when it is in contact.· The white has a small signal in mV but the grren when the beam is intacked it is around ·7v but when broken 0v.· I know that 7v is going to kill the pin so i regulated it down to 5v but when i tie it to a pin with a 220reistor it drops to 2.8v and if I rember correctly that is consider high.··· But this also baffles me why it drops to 2.8 volts.· Also why is the green and white hooke to + with a load im confused on this as well.· But when i use this in a pulsin command i can't get decent results.· What I mean is that i have to break the beam quickly for it to go of.· It flashes off then on and·then turns the solenoid on·But I need·is for it·to go off when it is broken and before it clears so to speak or engages the beam again.

At this point I am lost on what to do beside trying another photoswitch.

My program was simple sorry i forgot to make a copy before I left work.· But it was something like:
beam1 var word
main:
Pulsin 3,1,beam1
If beam1 = 0 then induction1
goto main

induction1:
high 14
pause 200
low 14
pause 20
goto main

Any help or comments would apperciated.

Thanks
Paul K.
·

daniel
07-28-2005, 10:29 AM
Paul,

The-electronics-guy said...

Also why is the green and white hooke to + with a load im confused on this as well.·
This photosensor has two switches, a normally open (NO) (Green Wire)·one and a normally closed (NC) (White Wire) one.· Each of these can switch a seperate load. When the photosensor detects the object, it closes the NO connection (turns·ON·the load connected to the Green·Wire) and it opens the NC connection (turns OFF the load connected to the White Wire).·

You should use only one of these loads for your application.· Make the choise based on·whether you want·the signal to the·pin to be HIGH or LOW to indicate the input.· If,·for rexample, you want your Stamp to see a HIGH signal when the photosensor detects the object, you would use the NO (Green Wire) connection.

When the NO switch closes, and the circuit is wired according to AB document, the LOAD experiences 24 VDC; that is, the +24VDC (from the Red Wire) tries to flow thru the load, thru the now-closed switch contact, to the ground (0 VDC) (on the Black Wire).

While there are several ways to proceed, I would recommend that your LOAD be a relay coil, rated for 24VDC.· Then use the contacts on the relay to switch the STAMP'S input pin to ground (one example of wiring the relays contacts can be derived from page 75 of the Industrial Control's (http://www.parallax.com/dl/docs/books/edu/ic.pdf (http://www.parallax.com/dl/docs/books/edu/ic.pdf))·book .·

Perhaps you might want to use the circuit at Ficure 105.2 in the N&V column http://www.parallax.com/dl/docs/cols/nv/vol5/col/nv105.pdf.· The screw terminals marked 12-36 VDC and GND are the LOAD according to the AB documentation; the isolated input to the stamp is also shown.· You will want to pay attention to the inverted nature of the STAMP's input.

This isolates the 24 VDC that the runs the photosensor from interacting with the Stamp's 5VDC circuits.


Finally, just check the input point for the desired signal, instead of attempting to count pulses in from the photosensor.

HTH,
Daniel


Post Edited (daniel) : 7/29/2005 2:02:42 AM GMT