[Starleper1]

What is a 2n7000?

[john-100]

Hi starleper1

the 2N7000 is a field effect transistor



to give you an idea of how the C3 board works I've drawn a cut down version of the board

when the photo transistor inside the sensors is in the dark

terminal C on the board will be pulled a high by a 1k0 resistor that is connected to +5V
terminal C will be at a high enough voltage to count as a logic 1 at the 74hc14 IC pin 1

this signal passes through two of the inverters inside of the 74hc14 IC
as a result pin 1 of the active high / active low selector is at a logic 0
and pin 3 is at a logic 1 ( the same as terminal C)

the signal connected by a jumper to pin 2 (passes through other inverters on the C3 board thats not shown)
is used to switch a NPN transistor on or off and provide the logic input to the final inverter thats connected to the TTL output selector pin3
the transistor collector is connected to the output selector pin 1
pin2 being connected to the output terminal block


the 180 ohm resistor limits the current flow from the +5v supply to terminal A
and then through the sensors LED to ground

with no obstruction between the LED and the Photo transistor

the photo transistor will conduct and the voltage at terminal C will drop to a low level (0.25 to 0.5V ?)

with more than one sensor connected
the LED's will not be as bright and the transistors pass less current
the terminal C may drop only to 1 or 2V
depending on the IC your actually using , the sensors may not switch the IC correctly or be more sensitive to electrical noise than expected


John

PS I've just looked at the 2N7000 data by adding a 1K0 pullup resistor between the 2N7000's gate terminal and +5v
the 2N7000 will be able to ground the breakout boards input when all the sensor transistors are switched off

this will work with breakout board TTL inputs or optoisolator inputs that only need the input to be switched to ground
inputs that need an active pull up to +5V will need an extra circuit adding

[neilw20]

You can't just put the leds in parallel.
One will rob the current from the others.
Fro 3 leds, putting the 3 in series, and using only a 10 ohm resistor should work fine from 5v. At least all the leds MUST have the same current then.
Measure the voltage across each, and you should all see a bit less than 2v on each.
Putting the outputs in parallel is OK.

[Starleper1]

I appreciate the suggestion and I was hopeful for the light at the end of the tunnel but I just went out and re-wired in series. Same result, only the Z axis sensor works. Obviously since everything is in series if I disconnect one sensor, then none will work. But with everything connected, like I said, only the Z works. I'm still getting only 0.2VDC from A-EK on the C3 board. Why is this one so much lower then all the rest?

I'm running out of solutions here.

Thanks again for all your help.

Here is how I re-wired the sensors in series.

[neilw20]

Now you have the sensors the wrong way.
On the left you need it like this.

D+ ... to 5v through a 10 ohm resistor.
+E ... all in parallel is the output.

You may have even destroyed one of the devices.
Trial leads to error.

Make sure all the leds measure OK with a multimeter on diode range.
Red to + and - to D will probably read about 1.8.
The other side might read anything depending on light getting into the sensor.

Always limit the current into leds or you can fry them.

[Starleper1]

Are you talking with or without the C3?

Can you draw a simple schematic showing what exactly you mean?

[neilw20]

3 sensors 1,2 and 3. are the numbers below.
You join the dots. Too hard to draw on the screen. You use a pencil. Best way to learn.

Connecting to the C3. Tell us ALL the numbers on the IC. Curiousity at work.

The LED side.
E/K to K1
+1 to K2 (leds in series)
+2 to K3
+3 to 10 ohm resistor.
other end of resistor to +5v (not A.) leave A unconnected. Resistor on the C3 too large to be of use for multiple sensors.

The sensor side.
E/K E1,E2 and E3.
C to C1,C2 and C3.

Block all sensor slits.
A should read close to 5v.

Unblock ANY sensor and A should read less than 1v.

[Starleper1]

Okay so we have progress. I connected the LED's in series with a 10ohm resistor to 5V. Now I can get any switch to work, as long as the other two are blocked.

For instance, as long as the X and Z are blocked, the Y axis works. Or as long as the X and Y are blocked the Z axis works. And so on....

Unfortunately I can't use them like this because the sensor is triggered by a spring loaded plunger that is held open. How can I make this work with my setup?

The numbers on the IC are 74ACT14N

[neilw20]

Simply put all the out puts in series, like the inputs are.
This makes the logic opposite.

[john-100]

Hi starleper1 ,

as I don't have any NTE3100 photo interuptor sensor switch or a C3 board

I have made some tests with an unmarked sensor that had been used on a lathe and a spare 74LS14 IC

from my tests without any sensor connected to your C3 board I'd expect the voltage
on terminal C to be +5V

if you select the active low jumper , the LED should only be on if you connect terminals C and E/K together

this will prove the C3 is OK


with a single working sensor connected and the slot blocked
terminal C should be at +5V
the sensors need to be in this state untill activated
when you have two or more sensors wired in parallel

with the sensor gap clear , the light from the sensors infra red diode will switch the transistor ON
the voltage on terminal C should now be about 0.2 or 0.3V
this is what you should have when a plunger is depressed
the C3 boards active low LED should also now be ON


its possible that a sensor could give you 1 to 4V on terminal C
either because the infra red LED current is too low and te reduced light level can not fully switch on the photo transistor ON when the plunger is depressed
or
you have light leaking past the moving vane when the plunger is NOT being depressed

tests indicate ambient light does not effect the sensor


If you pove the problem is because the LED current is too low with two or three sensors in parallel

to avoid changing the existing sensor wiring if the emitter and cathode wires are joined together at the sensor ( it will depend on the cable having 3 or 4 wires)

on two of the sensors I'd use extra 180 ohm resistors to connect the sensors A wire to +5V
(the third sensor being connected to the boards 180 ohm resistor on terminal A as normal )

John

[neilw20]

Sorry John,
But you are really complicating the issue.
My post should work.

[Starleper1]

So just to make sure I got this right.

Like this?

[neilw20]

Yes.

[Starleper1]

Disregard the LED side I forgot the change it with the 10ohm resistor. The output side is what I need to make sure is right.

[neilw20]

OK. Just add the 10 ohm resistor to the left side.
If any sensor gets shorted this will help stop the other 2 being destroyed.
May be it be 20 ohms, but if too high it will eventually not supply enough current.
You can always supply each led separately with a 220 ohm resistor on each one.
Depending on the LED characteristic it might need 6v instead of 5v.
A single resistor of 470 or 560 can be used and supply the led string from 12v.

[john-100]

Hi Neil

just attempting to verify what voltages you should have on a working NT3100 and what signal is needed by the C3 board
(the pictures of my test circuit can be ignored - they just show how I arrived at my result)

basically the control signal should be either at 0V or 5V (or some thing near)

a voltage half way between the two limits will be a problem


if wiring the sensors in series works thats great - just the result what we want

thats provided the sensors photo transistors are normally switched ON
and switch OFF when the plunger is pressed


John

[Starleper1]

IT WORKS!

Thank you to everyone who helped me out.

5V through a 10ohm resistor to the LED's in series, and putting outputs in series did the trick.

Thanks again

[neilw20]

KISS PRINCIPLE. Keep it simple stupid.

[john-100]

Hi starleper1

A good result :banana:

as predicted when all of the LED's are supplied with the correct current
the sensors will work correctly


John

[Al_The_Man]

First off I'd just like to thank you guys for all the tech support. I've gotten more troubleshooting done in this thread, than I have from the manufacturer of the board over emails.

.

Sad: Well it looks like it took almost 60 posts by members here to get a minor piece of retail equipment working that should, IMO, been cleared up by the supplier in short order? :devious:
Al.