couple questions regarding current draw.
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ok, application is COUNTing pulses from a Inductive Proximity sensor.
The sensor is running at 12.5v and spitting out 11.6v
I am lowering that voltage to 5v using a regulator (is that correct)?
it seems to be working fine, I'm using a 10k pulldown resistor to
zero the voltage... but not sure if thats too big.
reasong for thinking this, is, I'm using PIN9 for SEROUT, and PIN10
is one of my inputs, and PIN10 always mesures wrong.
PIN11, 12, 13, 14 and 15 are all fine.
I only have 1 sensor atm, so don't know if they are going to affect
each other..
My other concern on this project is, if I put the multimeter in line
from the regulator and the BS2e, its mesuring about 120mA.
should I be going for a lower voltage?
how could it possibly be drawing that much current?
am I mesuring it wrong?
TIA
The sensor is running at 12.5v and spitting out 11.6v
I am lowering that voltage to 5v using a regulator (is that correct)?
it seems to be working fine, I'm using a 10k pulldown resistor to
zero the voltage... but not sure if thats too big.
reasong for thinking this, is, I'm using PIN9 for SEROUT, and PIN10
is one of my inputs, and PIN10 always mesures wrong.
PIN11, 12, 13, 14 and 15 are all fine.
I only have 1 sensor atm, so don't know if they are going to affect
each other..
My other concern on this project is, if I put the multimeter in line
from the regulator and the BS2e, its mesuring about 120mA.
should I be going for a lower voltage?
how could it possibly be drawing that much current?
am I mesuring it wrong?
TIA
Comments
I think a regulator is definitely the wrong device to convert the
sensor voltage down to 5V!
These regulators are meant for power supply purposes and delivering
currents and not to convert (more or less current free) signal
voltages. You are going to fry your stamp this way (the 12V supply
voltage through the regulator into the stamp's pin which is a couple
of ohms input resistance).
I would use a pullup resistor to the input and a transistor to ground
and drive the base of the transistor through a resistor and may be a
voltage divider.
Regards
Adrian
Original Message
From: "emmertex" <emmertex@y...>
> The sensor is running at 12.5v and spitting out 11.6v
> I am lowering that voltage to 5v using a regulator (is that correct)?
Well, if it works, it works, but I would have thought a 5V zener or a
resistor would have been more appropriate.
- Robert
8K resistor in line from the output of the inductor, to the BS2, and
then a pulldown of about 3.9K going to earth?
that should supply me with about 1mA current at about 3.9v
is that correct.
or would you still reccomend going through the tranny for safety
reasons?
if I did do that.. how do I choose the transistor and do the math?
I'm sorry bout the stupid questions, its been a long time since I've
done anything with electronics, and I never knew that much to start
with
--- In basicstamps@yahoogroups.com, "Adrian Schneider"
<adrian.schneider@t...> wrote:
> Hi
>
> I think a regulator is definitely the wrong device to convert the
> sensor voltage down to 5V!
> These regulators are meant for power supply purposes and delivering
> currents and not to convert (more or less current free) signal
> voltages. You are going to fry your stamp this way (the 12V supply
> voltage through the regulator into the stamp's pin which is a
couple
> of ohms input resistance).
> I would use a pullup resistor to the input and a transistor to
ground
> and drive the base of the transistor through a resistor and may be
a
> voltage divider.
>
> Regards
> Adrian
What you mentionned is a simple voltage divider, in fact I wanted to
suggest that too. However, the stamp's inputs are low impedance, just
a couple of ohms (I don't remember how much exactly), so this
solution sould not work. That is why I brought up the transistor
variant - e.g. a 2n2222.
You might want to try this:
12V (sensor)
|
\8k
/
\
20k |
BS2----/\/
+
|
\3k9
/
\
_|_
Regards
Adrian
integrated opto-isolator/coupler with TTL digital O/P? That would
give the isolation as an extra and a bit of shaping via Schmitt
trigger. All in a neat 6 pin DIP package (eg H11L1).
Adrian
I have ordered the components for testing it to see how it goes.
thanks alot guys!
looks nice on the multimeter [noparse]:)[/noparse]
12V (sensor)
|
\ 6K7
/
\
18K |
BS2 ---/\/
+ NPN 2N2222
| |
\ /
/ 10K \ 3K9
\ /
|
|
|
-
---
Will be receiving about 800hz
--- In basicstamps@yahoogroups.com, "emmertex" <emmertex@y...> wrote:
> Thanks for those who helped me on this.
>
> I have ordered the components for testing it to see how it goes.
>
> thanks alot guys!