tapping the LED on a remote device
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I'm attempting to "tap" the line feeding an LED on a simple
standalone device using one of the general pins on a BS2.
I'd defined Pin1 (P1) on a BS2 as input, connected a wire from the
positive terminal of the LED to this pin and tested for P1 going to
the high state in my code. However, this test never succeeds (even
when power is supplied to the LED on the remote device).
I've tested the LED with my multimeter and it shows 1.77 V. Since the
BS2 requires 1.5V, I'd assumed that I'd have adequate voltage to
trigger the high-state on my input pin.
My hunch is that I've overlooked something very simple here. Any tips
or pointers appreciated.
Thanks!
--Donn
standalone device using one of the general pins on a BS2.
I'd defined Pin1 (P1) on a BS2 as input, connected a wire from the
positive terminal of the LED to this pin and tested for P1 going to
the high state in my code. However, this test never succeeds (even
when power is supplied to the LED on the remote device).
I've tested the LED with my multimeter and it shows 1.77 V. Since the
BS2 requires 1.5V, I'd assumed that I'd have adequate voltage to
trigger the high-state on my input pin.
My hunch is that I've overlooked something very simple here. Any tips
or pointers appreciated.
Thanks!
--Donn
Comments
> I'd defined Pin1 (P1) on a BS2 as input, connected a
> wire from the
> positive terminal of the LED to this pin and tested
> for P1 going to
> the high state in my code. However, this test never
> succeeds (even
> when power is supplied to the LED on the remote
> device).
Do you also have a "GROUND" reference from the device
with the LED? If not, the BS2 won't have a reference
point for the voltage coming from the LED...
Chris
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> --- donnmoidaho <donnmo@l...> wrote:
> > I'd defined Pin1 (P1) on a BS2 as input, connected a
> > wire from the
> > positive terminal of the LED to this pin and tested
> > for P1 going to
> > the high state in my code. However, this test never
> > succeeds (even
> > when power is supplied to the LED on the remote
> > device).
>
> Do you also have a "GROUND" reference from the device
> with the LED? If not, the BS2 won't have a reference
> point for the voltage coming from the LED...
>
> Chris
This was my thought as well. If these are two completely separate
circuits it would be good to have an optoisolator between then.
Appreciate the prompt reply. Have to plead ignorance--by ground
reference, are you saying that the negative terminal on the LED
should be tied to the ground in my BS2 circuit?
Thanks!
--Donn
--- In basicstamps@y..., Chris Savage <knight_designs@y...> wrote:
> --- donnmoidaho <donnmo@l...> wrote:
> > I'd defined Pin1 (P1) on a BS2 as input, connected a
> > wire from the
> > positive terminal of the LED to this pin and tested
> > for P1 going to
> > the high state in my code. However, this test never
> > succeeds (even
> > when power is supplied to the LED on the remote
> > device).
>
> Do you also have a "GROUND" reference from the device
> with the LED? If not, the BS2 won't have a reference
> point for the voltage coming from the LED...
>
> Chris
>
>
> __________________________________________________
> Do You Yahoo!?
> Yahoo! Health - Feel better, live better
> http://health.yahoo.com
> Chris,
> Appreciate the prompt reply. Have to plead
> ignorance--by ground
> reference, are you saying that the negative terminal
> on the LED
> should be tied to the ground in my BS2 circuit?
Yes (Preferrably if that's connected to the LED
circuit's ground). If that's all that's connected it
should work. A single wire won't supply any voltage
to the BS2 to detect the signal though. It'd be like
connecting a device to only one end of the battery...
Hope I helped...
Chris
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the LED to the BS2's ground. However, I fail to obtain a signal at
the input pin.
Interesting output on the multimeter (which is connected to the
positive line coming in to the BS2 as well as the BS2 ground). Not
sure what it might indicate:
1st reading: 24.2 mV
2nd reading: 90.0 mV
3rd reading: 222.7 mV
4th reading: 315.9 mV
5th reading: 385.3 mV
6th reading: 0 V
...
(This cycle repeats fairly consistently with flucations of +/- 1 mV.
The multimeter issues a new reading almost every second.)
Any tips or insight appreciated. (I'm a novice when it comes to
electronics and hardware.)
Thanks!
--Donn
--- In basicstamps@y..., Chris Savage <knight_designs@y...> wrote:
> --- donnmoidaho <donnmo@l...> wrote:
> > Chris,
> > Appreciate the prompt reply. Have to plead
> > ignorance--by ground
> > reference, are you saying that the negative terminal
> > on the LED
> > should be tied to the ground in my BS2 circuit?
>
> Yes (Preferrably if that's connected to the LED
> circuit's ground). If that's all that's connected it
> should work. A single wire won't supply any voltage
> to the BS2 to detect the signal though. It'd be like
> connecting a device to only one end of the battery...
>
> Hope I helped...
> Chris
>
>
>
> __________________________________________________
> Do You Yahoo!?
> Yahoo! Health - Feel better, live better
> http://health.yahoo.com
a data signal combined on a carrier wave block (mostly arround 40Khz)
to have less trouble with sun light or lighttubes
so to get the data you will have to filter out this block
Most common to drive a LED is by connecting one lead to the positve
voltage and the other to a transistor wich switches the ground
So if you tap directly accros the led you will get nothing !!!!
the ground of the stamp to the ground of your circuit and one
lead from the transistor side of the LED to the basic stamp input
!!!!!!!!!!!check to power supply voltage off your
circuit it should not be higher then the 5V of the max basicstamp input
other wise you need to bring this down ( resistor and a Zenerdiode)
Rene
PS. Ask off group for a schematic if you want one
Oorspronkelijk bericht
Van: donnmoidaho [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=xbbkwj0w1ce2g1pOVjKJFCBYzRIk-b7WS067zFvC8ZZx7icUGDfyEd3_zEl3CfRzPMN-oe3NrCzWIgEnHKY]donnmo@l...[/url
Verzonden: donderdag 25 juli 2002 22:31
Aan: basicstamps@yahoogroups.com
Onderwerp: [noparse][[/noparse]basicstamps] Re: tapping the LED on a remote device
I tested the complete circuit by connecting the negative terminal on
the LED to the BS2's ground. However, I fail to obtain a signal at
the input pin.
Interesting output on the multimeter (which is connected to the
positive line coming in to the BS2 as well as the BS2 ground). Not
sure what it might indicate:
1st reading: 24.2 mV
2nd reading: 90.0 mV
3rd reading: 222.7 mV
4th reading: 315.9 mV
5th reading: 385.3 mV
6th reading: 0 V
...
(This cycle repeats fairly consistently with flucations of +/- 1 mV.
The multimeter issues a new reading almost every second.)
Any tips or insight appreciated. (I'm a novice when it comes to
electronics and hardware.)
Thanks!
--Donn
--- In basicstamps@y..., Chris Savage <knight_designs@y...> wrote:
> --- donnmoidaho <donnmo@l...> wrote:
> > Chris,
> > Appreciate the prompt reply. Have to plead
> > ignorance--by ground
> > reference, are you saying that the negative terminal
> > on the LED
> > should be tied to the ground in my BS2 circuit?
>
> Yes (Preferrably if that's connected to the LED
> circuit's ground). If that's all that's connected it
> should work. A single wire won't supply any voltage
> to the BS2 to detect the signal though. It'd be like
> connecting a device to only one end of the battery...
>
> Hope I helped...
> Chris
>
>
>
> __________________________________________________
> Do You Yahoo!?
> Yahoo! Health - Feel better, live better
> http://health.yahoo.com
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> I tested the complete circuit by connecting the
> negative terminal on
> the LED to the BS2's ground. However, I fail to
> obtain a signal at
> the input pin.
Are you sure the polarity is correct? Try reversing
the leads on your meter next reading to see what you
get.
Chris
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