12 volt input?
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Posts: 46,084
How do I safely detect a higher voltage input with my basic stamp.
For instance:
+12 ----[noparse][[/noparse]switch]-- 12v power supply's neg (gnd)
|
|
a input on my basic stamp
Now, I know that is not a safe hookup... how should it be done?
For instance:
+12 ----[noparse][[/noparse]switch]-- 12v power supply's neg (gnd)
|
|
a input on my basic stamp
Now, I know that is not a safe hookup... how should it be done?
Comments
http://www.wd5gnr.com/stampfaq.htm, click on Hardware (on the left) and
look for the article titled: How can I read logic signals greater than
5V?
Al Williams
AWC
* Floating point math for the Stamp, PIC, SX, or any microcontroller
http://www.al-williams.com/awce/pak1.htm
>
Original Message
> From: GregT2 [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=Oh1OxwBEyVLOgVX4T6f_wsUnw7JWVfOQKHys9244xTgbKg31JogZKyJ2Ayi7PIi40pUUxWafZKgIpMI]gregt@t...[/url
> Sent: Saturday, September 21, 2002 4:26 PM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] 12 volt input?
>
>
> How do I safely detect a higher voltage input with my basic stamp.
>
> For instance:
>
> +12 ----[noparse][[/noparse]switch]-- 12v power supply's neg (gnd)
> |
> |
> a input on my basic stamp
>
> Now, I know that is not a safe hookup... how should it be done?
>
>
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>
Stamp.
Original Message
> How do I safely detect a higher voltage input with my basic stamp.
>
> For instance:
>
> +12 ----[noparse][[/noparse]switch]-- 12v power supply's neg (gnd)
> |
> |
> a input on my basic stamp
>
> Now, I know that is not a safe hookup... how should it be done?
12V ----[noparse][[/noparse] 10 K ]
+
[noparse][[/noparse] 4.7 K ]---- Ground
|
+
> Stamp pin
-- Jon Williams
-- Parallax
In a message dated 9/21/02 4:25:29 PM Central Daylight Time,
gregt@t... writes:
> How do I safely detect a higher voltage input with my basic stamp.
>
> For instance:
>
> +12 ----[noparse][[/noparse]switch]-- 12v power supply's neg (gnd)
> |
> |
> a input on my basic stamp
>
>
[noparse][[/noparse]Non-text portions of this message have been removed]
>
>For instance:
>
>+12 ----[noparse][[/noparse]switch]-- 12v power supply's neg (gnd)
> |
> |
> a input on my basic stamp
>
>Now, I know that is not a safe hookup... how should it be done?
You need a voltage divider to bring the 12 volts down to the Stamp level.
1M 690k
+12 on or off ---/\/\---o--/\/\---- ground
|
stamp pin P0
if P0=1 then ON12
An alternative would be an optoisolator:
1k
10k
+12 on or off ---/\/\--| |--o-/\/\-- +5 Vdd
| | |
|opto | '
P0
| |
12-
| |
Vss
If you want to measure the actual voltage, use a capacitor and RCtime:
1M 0.015uf
+12 ---/\/\---o----||---- ground
|
stamp pin P0
see http://www.emesys.com/BS2rct.htm#B_voltage
for more detail.
-- regards
Tracy Allen
electronically monitored ecosystems
http://www.emesystems.com
mailto:tracy@e...
I figured myself to use resistors to drop the voltage (ohms law), but
I'm having another problem. I think it's because I am using a
seperate voltage source and ground then the stamp is.
It seems to be confused about the input's state
(1 = on, 0 = off) Here is a sample of my debug window:
0 1 0 0 1 0 1 0 1 0 1 0 1 1 0 1 0 0 1 0 1 0
Now when I connect the stamp's ground to the 12v 's ground, I can get
the "on" position to work, but when the sensor is off it looks like
it does above.
This is a QS18VN6D optical sensor incase anyone knows anything about
it.
Greg
gregt@t... writes:
> Thanks for the help, but im still confused.
> I figured myself to use resistors to drop the voltage (ohms law), but
> I'm having another problem. I think it's because I am using a
> seperate voltage source and ground then the stamp is.
>
> It seems to be confused about the input's state
>
> (1 = on, 0 = off) Here is a sample of my debug window:
>
>
> 0 1 0 0 1 0 1 0 1 0 1 0 1 1 0 1 0 0 1 0 1 0
>
> Now when I connect the stamp's ground to the 12v 's ground, I can get
> the "on" position to work, but when the sensor is off it looks like
> it does above.
>
> This is a QS18VN6D optical sensor incase anyone knows anything about
> it.
>
> Greg
>
Greg:
Are you using the resistors in a voltage divider circuit, doing this will
keep the current through the resistors constant and will also maintain the
proper voltage into the input. It will be necessary to either use the same
ground with the stamp as the one you are using with the 12V circuit, this
shouldn't present a problem under normal circumstances, or, you will need to
us an optical isolator chip to interface the 12 V with the Stamp. You can
select an optical isolator that will allow you to use 12 V directly to it and
then use the isolated output of the chip to drive the input.
I hope this is of some help to you.
Randy Abernathy
4626 Old Stilesboro Road
Acworth, GA 30101
Ph / Fax: 770-974-5295
E-mail: cnc002@a...
We install, repair and service industrial CNC woodworking machinery. We
specialize in SCMI, SCM Group U.S.A. CNC panel saws and CNC routers.
[noparse][[/noparse]Non-text portions of this message have been removed]
necessary.
When you say "the sensor is off" do you mean you switch off the 12 volts, or
the do you mean when the sensor is not detecting anything??
According to the documentation, http://www.a-aelectric.com/pdfs/63908.pdf it
looks like this unit has an NPN output capable of sinking up to 100 ma. In
other words, you would normally have a load between the brown (bn) +12 wire
and the black (bk) *or* White (wh) wires (depending on if you wanted to
detect the presence or absence of an object) as shown in the leftmost
diagram on page 4. The blue (bu) wire would be ground, and this would also
be tied to Stamp ground.
If you use a voltage divider as others have mentioned, it would be your
load, and the total resistance would be such that the 100 ma limit would not
be exceeded. However, you should shoot for a much lower current since
dropping 12 volts at 100 ma would take some high-wattage resistors. I would
shoot for a much lower current (1-2 ma) so you could use 1/4 or 1/8 watt
resistors.
I would make up a voltage divider and test it with a power supply only (no
sensor or Stamp) to make sure things worked as planned before connecting it
up. The values Jon Williams mentioned would be fine, although I would also
insert a 330 ohm resistor between the Stamp pin and the voltage divider just
to prevent accidents.
Original Message
> Thanks for the help, but im still confused.
> I figured myself to use resistors to drop the voltage (ohms law), but
> I'm having another problem. I think it's because I am using a
> seperate voltage source and ground then the stamp is.
>
> It seems to be confused about the input's state
>
> (1 = on, 0 = off) Here is a sample of my debug window:
>
>
> 0 1 0 0 1 0 1 0 1 0 1 0 1 1 0 1 0 0 1 0 1 0
>
> Now when I connect the stamp's ground to the 12v 's ground, I can get
> the "on" position to work, but when the sensor is off it looks like
> it does above.
>
> This is a QS18VN6D optical sensor incase anyone knows anything about
> it.
I connected the stamp and 12v supply's ground (-) together through a
380ohm resistor. It works... but am i slowly destroying something?
This sensor is like those things in stores that beep when someone
walks in. They send out ir pulses, and recieve the reflections (or
sense if there isn't one). With the use of a old bike reflector it
works very well to tell if someone's been inside my room (or if a
switch is on, set of a alarm).
Thanks again for all the help, try and keep in mind that I dont
understand terms like "opto-isolator" (though I figured it out).
Greg
--- In basicstamps@y..., Rodent <daweasel@s...> wrote:
> Using an opto-isolator would allow you to keep the grounds
separate, if
> necessary.
>
> When you say "the sensor is off" do you mean you switch off the 12
volts, or
> the do you mean when the sensor is not detecting anything??
>
> According to the documentation, http://www.a-
aelectric.com/pdfs/63908.pdf it
> looks like this unit has an NPN output capable of sinking up to 100
ma. In
> other words, you would normally have a load between the brown (bn)
+12 wire
> and the black (bk) *or* White (wh) wires (depending on if you
wanted to
> detect the presence or absence of an object) as shown in the
leftmost
> diagram on page 4. The blue (bu) wire would be ground, and this
would also
> be tied to Stamp ground.
>
> If you use a voltage divider as others have mentioned, it would be
your
> load, and the total resistance would be such that the 100 ma limit
would not
> be exceeded. However, you should shoot for a much lower current
since
> dropping 12 volts at 100 ma would take some high-wattage resistors.
I would
> shoot for a much lower current (1-2 ma) so you could use 1/4 or 1/8
watt
> resistors.
>
> I would make up a voltage divider and test it with a power supply
only (no
> sensor or Stamp) to make sure things worked as planned before
connecting it
> up. The values Jon Williams mentioned would be fine, although I
would also
> insert a 330 ohm resistor between the Stamp pin and the voltage
divider just
> to prevent accidents.
>
>
>
Original Message
>
>
> > Thanks for the help, but im still confused.
> > I figured myself to use resistors to drop the voltage (ohms law),
but
> > I'm having another problem. I think it's because I am using a
> > seperate voltage source and ground then the stamp is.
> >
> > It seems to be confused about the input's state
> >
> > (1 = on, 0 = off) Here is a sample of my debug window:
> >
> >
> > 0 1 0 0 1 0 1 0 1 0 1 0 1 1 0 1 0 0 1 0 1 0
> >
> > Now when I connect the stamp's ground to the 12v 's ground, I can
get
> > the "on" position to work, but when the sensor is off it looks
like
> > it does above.
> >
> > This is a QS18VN6D optical sensor incase anyone knows anything
about
> > it.
too high a voltage on the Stamp pin. I suspect the input voltage on your
Stamp pin was too high and the resistor corrected it in a round-about way.
Original Message
> Here is what I did, tell me if its bad.
>
> I connected the stamp and 12v supply's ground (-) together through a
> 380ohm resistor. It works... but am i slowly destroying something?
>
> This sensor is like those things in stores that beep when someone
> walks in. They send out ir pulses, and recieve the reflections (or
> sense if there isn't one). With the use of a old bike reflector it
> works very well to tell if someone's been inside my room (or if a
> switch is on, set of a alarm).
>
> Thanks again for all the help, try and keep in mind that I dont
> understand terms like "opto-isolator" (though I figured it out).
>
> Greg
>
> --- In basicstamps@y..., Rodent <daweasel@s...> wrote:
> > Using an opto-isolator would allow you to keep the grounds
> separate, if
> > necessary.
> >
> > When you say "the sensor is off" do you mean you switch off the 12
> volts, or
> > the do you mean when the sensor is not detecting anything??
> >
> > According to the documentation, http://www.a-
> aelectric.com/pdfs/63908.pdf it
> > looks like this unit has an NPN output capable of sinking up to 100
> ma. In
> > other words, you would normally have a load between the brown (bn)
> +12 wire
> > and the black (bk) *or* White (wh) wires (depending on if you
> wanted to
> > detect the presence or absence of an object) as shown in the
> leftmost
> > diagram on page 4. The blue (bu) wire would be ground, and this
> would also
> > be tied to Stamp ground.
> >
> > If you use a voltage divider as others have mentioned, it would be
> your
> > load, and the total resistance would be such that the 100 ma limit
> would not
> > be exceeded. However, you should shoot for a much lower current
> since
> > dropping 12 volts at 100 ma would take some high-wattage resistors.
> I would
> > shoot for a much lower current (1-2 ma) so you could use 1/4 or 1/8
> watt
> > resistors.
> >
> > I would make up a voltage divider and test it with a power supply
> only (no
> > sensor or Stamp) to make sure things worked as planned before
> connecting it
> > up. The values Jon Williams mentioned would be fine, although I
> would also
> > insert a 330 ohm resistor between the Stamp pin and the voltage
> divider just
> > to prevent accidents.
> >
> >
> >
Original Message
> >
> >
> > > Thanks for the help, but im still confused.
> > > I figured myself to use resistors to drop the voltage (ohms law),
> but
> > > I'm having another problem. I think it's because I am using a
> > > seperate voltage source and ground then the stamp is.
> > >
> > > It seems to be confused about the input's state
> > >
> > > (1 = on, 0 = off) Here is a sample of my debug window:
> > >
> > >
> > > 0 1 0 0 1 0 1 0 1 0 1 0 1 1 0 1 0 0 1 0 1 0
> > >
> > > Now when I connect the stamp's ground to the 12v 's ground, I can
> get
> > > the "on" position to work, but when the sensor is off it looks
> like
> > > it does above.
> > >
> > > This is a QS18VN6D optical sensor incase anyone knows anything
> about
> > > it.