Bs2p for 1 wire for RH sensor
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Paul-
As others have pointed out, your ground wire is connected to your
Stamp's ground, and the data/power wire is connected to your Stamp's
1-Wire bus I/O pin. The bus I/O pin is also pulled up by a
(typically) 4.7 K resistor to +5 V. Your Stamp and your 1-Wire
device (humidity sensor in this case) talk to each other by driving
the 1-Wire bus low with short pulses (the BS2p one wire commands
handle all this for you). During idle bus periods, the 1-Wire
devices steal and store a bit of power from the bus (via the pullup
resistor to +5 V) so they can operate during the brief lows on the
bus.
Assuming you're using the DSHS01K sensor, you may want to replace the
garden-variety 4.7 K resistor with a 1.5 K resistor. The DSHS01K
continuously draws enough current (~0.15 mA for the HIH-3610 alone)
through the pullup resistor to cause an appreciable voltage drop
across a 4.7 K resistor, resulting in a relatively low voltage on
the open-drain bus. Changing the resistor to a lower value gives
you a more nominal idle bus voltage. This can become more important
if you also have a bunch of other 1-Wire devices (thermometers or
whatever) on the same bus, all trying to derive power from, and
detect logic level changes on the bus. The Dallas documentation
does not recommend going lower than 1.5 K ohms.
On 7 Mar 01 at 7:12, Paul Verhage wrote:
> I have a one wire relative humidity sensor from Dallas. This device
> has a single wire for ground and a second wire for data/power. How
> on earth is this wired up to the BS2P? Will the BS2P provide power
> for the sensor through the I/O pin? Is there a way to wire power to
> the device through some sort of pull up?
>
> Thanks,
> Paul
>
>
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
>
>
As others have pointed out, your ground wire is connected to your
Stamp's ground, and the data/power wire is connected to your Stamp's
1-Wire bus I/O pin. The bus I/O pin is also pulled up by a
(typically) 4.7 K resistor to +5 V. Your Stamp and your 1-Wire
device (humidity sensor in this case) talk to each other by driving
the 1-Wire bus low with short pulses (the BS2p one wire commands
handle all this for you). During idle bus periods, the 1-Wire
devices steal and store a bit of power from the bus (via the pullup
resistor to +5 V) so they can operate during the brief lows on the
bus.
Assuming you're using the DSHS01K sensor, you may want to replace the
garden-variety 4.7 K resistor with a 1.5 K resistor. The DSHS01K
continuously draws enough current (~0.15 mA for the HIH-3610 alone)
through the pullup resistor to cause an appreciable voltage drop
across a 4.7 K resistor, resulting in a relatively low voltage on
the open-drain bus. Changing the resistor to a lower value gives
you a more nominal idle bus voltage. This can become more important
if you also have a bunch of other 1-Wire devices (thermometers or
whatever) on the same bus, all trying to derive power from, and
detect logic level changes on the bus. The Dallas documentation
does not recommend going lower than 1.5 K ohms.
On 7 Mar 01 at 7:12, Paul Verhage wrote:
> I have a one wire relative humidity sensor from Dallas. This device
> has a single wire for ground and a second wire for data/power. How
> on earth is this wired up to the BS2P? Will the BS2P provide power
> for the sensor through the I/O pin? Is there a way to wire power to
> the device through some sort of pull up?
>
> Thanks,
> Paul
>
>
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
>
>
Comments
single wire for ground and a second wire for data/power. How on earth is
this wired up to the BS2P? Will the BS2P provide power for the sensor
through the I/O pin? Is there a way to wire power to the device through
some sort of pull up?
Thanks,
Paul
Robert Staph, KB3FXS
The Center for Advanced Technologies
Original Message
From: Paul Verhage <pverhage@s...>
To: <basicstamps@yahoogroups.com>
Sent: Wednesday, March 07, 2001 9:12 AM
Subject: RE: [noparse][[/noparse]basicstamps] Bs2p for 1 wire for RH sensor
> I have a one wire relative humidity sensor from Dallas. This device has a
> single wire for ground and a second wire for data/power. How on earth is
> this wired up to the BS2P? Will the BS2P provide power for the sensor
> through the I/O pin? Is there a way to wire power to the device through
> some sort of pull up?
>
> Thanks,
> Paul
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
pverhage@sd131.k12.id.us writes:
single wire for ground and a second wire for data/power. ·How on earth is
this wired up to the BS2P? ·Will the BS2P provide power for the sensor
through the I/O pin? ·Is there a way to wire power to the device through
some sort of pull up?
The 1-Wire bus (where the data/power coonection is made) must be pulled-up to
+5 volts through a 4.7K resistor. ·[/font]
> I have a one wire relative humidity sensor from Dallas. This device has a
> single wire for ground and a second wire for data/power. How on earth is this
> wired up to the BS2P? Will the BS2P provide power for the sensor through the
> I/O pin? Is there a way to wire power to the device through some sort of pull
> up?
>
> Thanks,
> Paul
>
Most of the Dallas 1 wire stuff gets power of the buss. Devices with time
keeping have an internal 10 year Lithium battery. The Thermochron also
uses the battery for temperature readings. Note you always need 2
connections, 1 wire and ground.