Parallel High speed inputs

[carl]

I'm having a problem using a pulse to input a TI high speed counter and a Red Lion display at the same time. Input device is a NPN type open collector. Been to Red Lion with this and their suggestions didn't work. When the input is paralleled to both devices the display doesn't work. They each will work if connected separately. I am considering using a signal conditioning relay that will provide a pulse to the display when the meter output is off. What do you think?
Thanks
Carl

[dorian]

I don't know the devices you are using but you can try to use two buffers 74ls07, to get two open colector outputs

[Tom Jenkins]

Have you compare the min/max load ratings of the device providing the pulse with the resulting load from the T1 and Red Lion in parallel?

[carl]

Dorian,
I haven't the foggiest what buffers you are talking about. Could you please explain?
Tom,
Unfortunately I have no info on the pulse meter. I contacted the supplier and found they didn't build it and no longer support it.
Next opportunity I plan on trying to add the relay in parallel with each of the input devices.
Thank You both for your reply. I'll post my results.
Carl

[Steve Etter]

I know its a real shot in the dark, but what is the model number of the Red Lion display. I have a catalog from 1997 (not real old, but what the heck) that might have some useful info.

[carl]

Thanks Takoga,
I don't have them at home but I have all the booklets on the display and the TI high speed counter module.The display is selectable for most any kind of input using dip switches. I got a response from thier tech support on the issue but the scheme didn't work.I hope to try a couple of things soon.
Thank you for your post.
Carl

[Eric Nelson]

It probably doesn't take much current to turn on either of the inputs, so one probably leaks enough current to turn on the other one.

The simplest solution would be to use a diode feeding each input to isolate them from each other like this:

DIODE
----|>|-----> RED LION INPUT
|
|
SENSOR OUTPUT>------|
|
| DIODE
----|>|-----> TI HSC INPUT



What kind of diode? 1N4001's will work fine here.

-Eric

[carl]

Thanks Eric I can try that.
Carl

[dorian]

74ls07 ( or SN74ls07 )is a TTL IC hex buffer non inverting width open colector outputs:
pin 1-buffer1 input - pulse output
pin 2-buffer1 output- red lion input
pin 3-buffer2 input - pulse output
pin 4-buffer3 output- hsc input
pin 7- GND
pin 14- +5V (VCC)
you can find the datasheet here : http://onyx.boisestate.edu/~jcofflan/CPM/datasheets/74LS07.pdf

If still doesn't work you may have troubles width electrical insulation between hsc and red lion.

[carl]

Thank You Dorian, I
will look into the buffer.
Carl

[sid]

Without knowing exactly what type of input device you are
using, or the mechanical configuration this may not work for
you, depending on how accurately the two need to track each other.
I have used two pickup devices, one for each unit and connected
them to the same shaft in the case of encoders and in a parallel
bracket support for prox. type devices. Then I would use two
dry type contacts to reset both devices at the same time.