serial communication voltages
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In a message dated 7/15/2004 2:59:24 PM Eastern Daylight Time,
randyjones@w... writes:
> Another option would be to use a series 2-resistor voltage divider
> connected
> to each Stamp output pin to drop the +5V output to +3.3V. The selection of
> resistor values might depend somewhat on the input characteristics of the
>
Digikey has a little pot that does a great job for something like this -
3006K-302 - single turn, $0.57 each.
Sid
[noparse][[/noparse]Non-text portions of this message have been removed]
randyjones@w... writes:
> Another option would be to use a series 2-resistor voltage divider
> connected
> to each Stamp output pin to drop the +5V output to +3.3V. The selection of
> resistor values might depend somewhat on the input characteristics of the
>
Digikey has a little pot that does a great job for something like this -
3006K-302 - single turn, $0.57 each.
Sid
[noparse][[/noparse]Non-text portions of this message have been removed]
Comments
device. However, the other device wants the voltage of the serial
signal to be a maximum of 3.3v, and the stamp puts out 5v. There's
only 3 wires that go from the stamp to the other device: Data, Clock,
and Enable. Is there an easy way to lower the voltage so my serial
device will accept the serial signals?
Thanks,
Andy
just under that Voltage. Then use a series limiting resistor, say of 1.0 k
Ohm.
5 Volt Signal out
resistor
input to your device
-
-
zener
diode
-
-
-
system ground
Original Message
From: andy_watson5 [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=WYTVoe82CMf64su65L33l7lBPzX3P5uqYvR5JE0g29inMkatQ1wItHW_aKUcKb-iIs-8ZyTPoHoCQUxDtg]andywatson@m...[/url
Sent: Thursday, July 15, 2004 1:40 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] serial communication voltages
I'm trying to get my BS2p40 to SHIFTOUT some serial data to another device.
However, the other device wants the voltage of the serial signal to be a
maximum of 3.3v, and the stamp puts out 5v. There's only 3 wires that go
from the stamp to the other device: Data, Clock, and Enable. Is there an
easy way to lower the voltage so my serial device will accept the serial
signals?
Thanks,
Andy
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--- In basicstamps@yahoogroups.com, "Grover Richardson"
<grover.richardson@g...> wrote:
> Use a zener diode of 3.3 Volts. Or a stack of diodes, forward
biased, to
> just under that Voltage. Then use a series limiting resistor, say
of 1.0 k
> Ohm.
>
>
>
> 5 Volt Signal out
resistor
input to your device
> -
> -
> zener
> diode
> -
> -
> -
> system ground
>
>
Original Message
> From: andy_watson5 [noparse][[/noparse]mailto:andywatson@m...]
> Sent: Thursday, July 15, 2004 1:40 PM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] serial communication voltages
>
>
> I'm trying to get my BS2p40 to SHIFTOUT some serial data to another
device.
> However, the other device wants the voltage of the serial signal to be a
> maximum of 3.3v, and the stamp puts out 5v. There's only 3 wires
that go
> from the stamp to the other device: Data, Clock, and Enable. Is
there an
> easy way to lower the voltage so my serial device will accept the serial
> signals?
>
> Thanks,
> Andy
>
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the
Subject and
> Body of the message will be ignored.
>
> Yahoo! Groups Links
Another option would be to use a series 2-resistor voltage divider connected
to each Stamp output pin to drop the +5V output to +3.3V. The selection of
resistor values might depend somewhat on the input characteristics of the
device receiving the data, but this should be a reasonable starting point:
Connect one end of a 1.0k ohm resistor to the Stamp I/O pin, and the other
end to one end of a 2.0k resistor. The other end of the 2.0k resistor is
connected to ground. Connect the point where the two resistors are joined
together to the input pin of the other device. Do the same thing on all
three Stamp pins.
When you apply the 5V signal from the Stamp I/O pin to the 2-resistor
voltage divider, the output voltage from the junction of the two resistors
will be the resistance of the bottom resistor (2.0k) divided by the total
resistance (3.0k) multiplied by the source voltage (5V). So you'll get
about 2/3*5.0V = 3.3V.
You don't have to use 1.0k and 2.0k resistors as long as the ratio remains
correct. But... If the resistor values are too large, they may not be able
to supply enough drive power for the other device's input requirements. If
the values are too low, quite a bit of current will be drawn from the Stamp
pin and it will no longer provide ~5V.
A little experimenting should provide the voltage you need. It would be
wise to measure the voltage output at the resistor junctions with the
combination you're trying before connecting to the receiving device's input
pins (to make sure it's not over 3.3V).
-Randy
www.glitchbuster.com
Original Message
From: "andy_watson5" <andywatson@m...>
To: <basicstamps@yahoogroups.com>
Sent: Thursday, July 15, 2004 10:39 AM
Subject: [noparse][[/noparse]basicstamps] serial communication voltages
> I'm trying to get my BS2p40 to SHIFTOUT some serial data to another
> device. However, the other device wants the voltage of the serial
> signal to be a maximum of 3.3v, and the stamp puts out 5v. There's
> only 3 wires that go from the stamp to the other device: Data, Clock,
> and Enable. Is there an easy way to lower the voltage so my serial
> device will accept the serial signals?
>
> Thanks,
> Andy
>
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
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Body of the message will be ignored.
>
> Yahoo! Groups Links
>
>
>
>
>
device.
Another reader also mentioned a simple Voltage divider. That will work
also. I like to use the Zener diode to ensure that I will have a maximum
limited Voltage. We have spikes around here<G>.
Original Message
From: andy_watson5 [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=HY7LSJwnl-oEEIAySRI73CASB3J4PKcWTZkoqQmizlQilbLFQtgKjHiwqFQXxV2Jcyi6mtFDo7TMP2O5Mw]andywatson@m...[/url
Sent: Thursday, July 15, 2004 2:15 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Re: serial communication voltages
Thanks. Do I put this configuration on all 3 output pins of the stamp?
--- In basicstamps@yahoogroups.com, "Grover Richardson"
<grover.richardson@g...> wrote:
> Use a zener diode of 3.3 Volts. Or a stack of diodes, forward
biased, to
> just under that Voltage. Then use a series limiting resistor, say
of 1.0 k
> Ohm.
>
>
>
> 5 Volt Signal out
resistor
input to your device
> -
> -
> zener
> diode
> -
> -
> -
> system ground
>
>
Original Message
> From: andy_watson5 [noparse][[/noparse]mailto:andywatson@m...]
> Sent: Thursday, July 15, 2004 1:40 PM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] serial communication voltages
>
>
> I'm trying to get my BS2p40 to SHIFTOUT some serial data to another
device.
> However, the other device wants the voltage of the serial signal to be
> a maximum of 3.3v, and the stamp puts out 5v. There's only 3 wires
that go
> from the stamp to the other device: Data, Clock, and Enable. Is
there an
> easy way to lower the voltage so my serial device will accept the
> serial signals?
>
> Thanks,
> Andy
>
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the
Subject and
> Body of the message will be ignored.
>
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