Digital Potentiometers
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Posts: 46,084
For a circuit I found in the Microcontroller Application Cookbook, I
recently picked up a DS1804 digital potentiometer. I connected it to my
BS2 and to an a VOM and it works.
At the same time I bought a DS1267 digital pot. I have not yet attempted
to use it. It turns out the methods for moving the wipers are quite
different. For the 1804s, the program simply increments (and
decrements) by pulsing high and low.
For the 1267 series the command SHIFTOUT could be used, I suspect, to
specify a wiper position. The 1267 approach seems better for my
application, because I think it will jump the wiper from position to
position. With the 1804, it seems necessary to walk the wiper though all
the intermediate positions.
The hope is, the 1267 program would be faster at changing the resistance
of the pot. On the other hand, the SHIFTOUT command and serial transfer
be slow -- I have never used it. (My BS2 is 2 weeks old).
Has anyone worked with the 1267? Is there any sample code for making it
go? (Dallas semi has some code for an 8081, but does not have anything
published on using the 1267 pot with a BS2.
Also, I was wondering if I can regard the resistance element and wiper
as completely isolated from the circuitry of the BS2. It have it in
mind to replace, with the 1267 or the 1804, the joystick pot of an R/C
transmitter.
Many thanks for your insights on this. Michael Gianturco
recently picked up a DS1804 digital potentiometer. I connected it to my
BS2 and to an a VOM and it works.
At the same time I bought a DS1267 digital pot. I have not yet attempted
to use it. It turns out the methods for moving the wipers are quite
different. For the 1804s, the program simply increments (and
decrements) by pulsing high and low.
For the 1267 series the command SHIFTOUT could be used, I suspect, to
specify a wiper position. The 1267 approach seems better for my
application, because I think it will jump the wiper from position to
position. With the 1804, it seems necessary to walk the wiper though all
the intermediate positions.
The hope is, the 1267 program would be faster at changing the resistance
of the pot. On the other hand, the SHIFTOUT command and serial transfer
be slow -- I have never used it. (My BS2 is 2 weeks old).
Has anyone worked with the 1267? Is there any sample code for making it
go? (Dallas semi has some code for an 8081, but does not have anything
published on using the 1267 pot with a BS2.
Also, I was wondering if I can regard the resistance element and wiper
as completely isolated from the circuitry of the BS2. It have it in
mind to replace, with the 1267 or the 1804, the joystick pot of an R/C
transmitter.
Many thanks for your insights on this. Michael Gianturco
Comments
I saw where you can get samples and literature. They have a great site loaded
with lots of information.
I received a pair of ds1804's in the mail yesterday.
John
http://dbserv.maxim-ic.com/sl_requests2.cfm
REQUEST SAMPLES
You can order Dallas Semiconductor and Maxim samples via web, phone, or fax. You
can request up to eight part numbers. We will send you two samples of each part.
Note: Samples are intended for evaluating product performance, suitability for
an application, and for building prototypes. They are not intended for
reliability testing, for long-term testing or use, and they should not be
incorporated into equipment to be sold. Maxim's samples are fully functional and
are tested to the same electrical specifications as parts we sell, but may be
older or may not have the same reliability expectations as parts we sell.
Michael Gianturco <michcg@m...> wrote:
>For a circuit I found in the Microcontroller Application Cookbook, I
>recently picked up a DS1804 digital potentiometer. I connected it to my
>BS2 and to an a VOM and it works.
>
>At the same time I bought a DS1267 digital pot. I have not yet attempted
>to use it. It turns out the methods for moving the wipers are quite
>different. For the 1804s, the program simply increments (and
>decrements) by pulsing high and low.
>
>For the 1267 series the command SHIFTOUT could be used, I suspect, to
>specify a wiper position. The 1267 approach seems better for my
>application, because I think it will jump the wiper from position to
>position. With the 1804, it seems necessary to walk the wiper though all
>the intermediate positions.
>
>The hope is, the 1267 program would be faster at changing the resistance
>of the pot. On the other hand, the SHIFTOUT command and serial transfer
>be slow -- I have never used it. (My BS2 is 2 weeks old).
>
>Has anyone worked with the 1267? Is there any sample code for making it
>go? (Dallas semi has some code for an 8081, but does not have anything
>published on using the 1267 pot with a BS2.
>
>Also, I was wondering if I can regard the resistance element and wiper
>as completely isolated from the circuitry of the BS2. It have it in
>mind to replace, with the 1267 or the 1804, the joystick pot of an R/C
>transmitter.
>
>Many thanks for your insights on this. Michael Gianturco
>
>
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lego motors with my stamp. I was able to figure out how to use an electronic
switch controlled by the stamp to control power to the motor, but my next
wish is to control the amount of power. So I thought I could use a digital
potentiometer, which I learned about in the parallax "what is a
microcomputer" module.
I tried using the potentiometer that came with that (100K in 1K steps) and
nothing happenned, so I wound up checking the resistance of my lego motor and
found out it is very low. If I use a resistance of 40 or less ohms I can
get results. so I looked for a digital potentiometer that low.
I found one on digi-key (I think) - the DS1845E-020-ND, which seems to be 250
ohms in 100 steps. I am pretty new to digital potentiometers and the one in
the "what is a microcomputer" module was an "increment/decrement" interface,
whereas this one is a 2 wire interface, which I know nothing about.
How can I learn about the different interfaces for digital potentiometers and
other info that may be important for me to know so I can make reasonably
informed decisions about this
thanks
consume maybe 1 /100th of the power the motor does. If you try to run a
motor with them you will burn up the pot.
What you need is an H-bridge circuit or module. This allows you to turn the
motor on / off and reverse direction, as well as controlling the speed by
turning the motor on / off rapidly. You can build the circuit from scratch
or buy one from various vendors. For small motors the Allegro modules are
easy to use. www.allegromicro.com.
Original Message
> I am trying, with limited knowledge (which makes it more fun!) to control
my
> lego motors with my stamp. I was able to figure out how to use an
electronic
> switch controlled by the stamp to control power to the motor, but my next
> wish is to control the amount of power. So I thought I could use a
digital
> potentiometer, which I learned about in the parallax "what is a
> microcomputer" module.
>
> I tried using the potentiometer that came with that (100K in 1K steps) and
> nothing happenned, so I wound up checking the resistance of my lego motor
and
> found out it is very low. If I use a resistance of 40 or less ohms I can
> get results. so I looked for a digital potentiometer that low.
>
> I found one on digi-key (I think) - the DS1845E-020-ND, which seems to be
250
> ohms in 100 steps. I am pretty new to digital potentiometers and the one
in
> the "what is a microcomputer" module was an "increment/decrement"
interface,
> whereas this one is a 2 wire interface, which I know nothing about.
>
> How can I learn about the different interfaces for digital potentiometers
and
> other info that may be important for me to know so I can make reasonably
> informed decisions about this
You can get sample IC's from www.alegromicro.com in small amounts usually
2-6 of one type.
Also www.ti.com offers a similar service for 2-4 samples. It took about 1 week
to get the samples I ordered and
it cost was $0.00, give them a try. I used Robotics Hobbyist as my application
in their application for the
IC's. I am about ready to use 2 of these samples in a small robot I am
building. Look at the data sheets before
you order so that you can get the right part(s) for your project.
Having Fun !!
Dale Fleischmann
Rodent wrote:
> A digital pot is not what you want to use. They are made for circuits which
> consume maybe 1 /100th of the power the motor does. If you try to run a
> motor with them you will burn up the pot.
>
> What you need is an H-bridge circuit or module. This allows you to turn the
> motor on / off and reverse direction, as well as controlling the speed by
> turning the motor on / off rapidly. You can build the circuit from scratch
> or buy one from various vendors. For small motors the Allegro modules are
> easy to use. www.allegromicro.com.
>
>
Original Message
>
> > I am trying, with limited knowledge (which makes it more fun!) to control
> my
> > lego motors with my stamp. I was able to figure out how to use an
> electronic
> > switch controlled by the stamp to control power to the motor, but my next
> > wish is to control the amount of power. So I thought I could use a
> digital
> > potentiometer, which I learned about in the parallax "what is a
> > microcomputer" module.
> >
> > I tried using the potentiometer that came with that (100K in 1K steps) and
> > nothing happenned, so I wound up checking the resistance of my lego motor
> and
> > found out it is very low. If I use a resistance of 40 or less ohms I can
> > get results. so I looked for a digital potentiometer that low.
> >
> > I found one on digi-key (I think) - the DS1845E-020-ND, which seems to be
> 250
> > ohms in 100 steps. I am pretty new to digital potentiometers and the one
> in
> > the "what is a microcomputer" module was an "increment/decrement"
> interface,
> > whereas this one is a 2 wire interface, which I know nothing about.
> >
> > How can I learn about the different interfaces for digital potentiometers
> and
> > other info that may be important for me to know so I can make reasonably
> > informed decisions about this
>
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of the message will be ignored.
>
>
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[noparse][[/noparse]Non-text portions of this message have been removed]
>
Original Message
>
>> I am trying, with limited knowledge (which makes it more fun!) to
control
>my
>> lego motors with my stamp. I was able to figure out how to use an
>electronic
>> switch controlled by the stamp to control power to the motor, but
my next
>> wish is to control the amount of power. So I thought I could use a
>digital
>> potentiometer, which I learned about in the parallax "what is a
>> microcomputer" module.
>>
>> I tried using the potentiometer that came with that (100K in 1K
steps) and
>> nothing happenned, so I wound up checking the resistance of my lego
motor
>and
>> found out it is very low. If I use a resistance of 40 or less
ohms I can
>> get results. so I looked for a digital potentiometer that low.
>>
>> I found one on digi-key (I think) - the DS1845E-020-ND, which seems
to be
>250
>> ohms in 100 steps. I am pretty new to digital potentiometers and
the one
>in
>> the "what is a microcomputer" module was an "increment/decrement"
>interface,
>> whereas this one is a 2 wire interface, which I know nothing about.
>>
>> How can I learn about the different interfaces for digital
potentiometers
>and
>> other info that may be important for me to know so I can make
reasonably
>> informed decisions about this
>
If all you want to do is run the motor in one direction.....a simple
and cheap way is to use a power mosfet(a dollar or two) and control
the power level to the motor with the PWM command. I can send you a
very simple circuit schematic if you are interested.
Paul Lugger
__________________________________________________________________
Get your free Australian email account at http://www.start.com.au
Ideally you would want to use a motor controller IC like a L298, L293,
Allegro A2951, SN754410.
A simpler approach is to use a hobby RC servo and have it control a Car RC
hobby reostat resistor or sliding switch matrix. Then you can send simple
PWM pulses to the servo to control the motors. These should be very easy to
get at a RC hobby shop in your area, or through www.towerhobbies.com.
If the motors aren't too powerful, you could simply use a transistor Hbridge
as well. Some 2n2222 and 2n2903 transistors would do the trick. If the motor
only needs to run one direction you could simply use a single transistor
like a MOSFET IRF540 IRF9540, or a darlingtion like a TIP120 or TIP125 to
turn the motor on or off. www.dprg.org has a couple of motor control
circuits that may be of interest to you.
Original Message
From: eclecticrr@A... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=qNXeKFY9fXM0dmi90vXRv2v5tHJW4DG-FyQR28HzLZQXYX8qvXMkJDCBw_7O4WcuR2AirSlR4c8]eclecticrr@A...[/url
Sent: Saturday, May 11, 2002 10:48 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] digital potentiometers
I am trying, with limited knowledge (which makes it more fun!) to control my
lego motors with my stamp. I was able to figure out how to use an
electronic
switch controlled by the stamp to control power to the motor, but my next
wish is to control the amount of power. So I thought I could use a digital
potentiometer, which I learned about in the parallax "what is a
microcomputer" module.
I tried using the potentiometer that came with that (100K in 1K steps) and
nothing happenned, so I wound up checking the resistance of my lego motor
and
found out it is very low. If I use a resistance of 40 or less ohms I can
get results. so I looked for a digital potentiometer that low.
I found one on digi-key (I think) - the DS1845E-020-ND, which seems to be
250
ohms in 100 steps. I am pretty new to digital potentiometers and the one in
the "what is a microcomputer" module was an "increment/decrement" interface,
whereas this one is a 2 wire interface, which I know nothing about.
How can I learn about the different interfaces for digital potentiometers
and
other info that may be important for me to know so I can make reasonably
informed decisions about this
thanks
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MLX10402, to Lego to do this job. Ask Melexis for a sample thu their web
site. Hope this helps.
Chuck
'setup for a Melexis MLX10402 motor switcher
'and Lego 9v motor
'5/1/00
b1=9 'stamp pins 9 and 10 connected to Melexis inputs
b2=10
aa: 'speed increase in one direction and
low b1 'speed increase in reverse direction
low b2
for b0=50 to 250
pwm b1,b0,100
pause 5
next
pause 5000
if b1=9 then cc
b1=9:b2=10
goto aa
cc:
b1=10:b2=9
goto aa
How do you ask for a sample?
It sounds like a good approach if the chip is made specifically for this
purpose.
thanks
In a message dated 05/13/2002 7:59:08 AM Pacific Daylight Time,
CHIPKEN@a... writes:
<<
Below is some pbasic code to control your Lego motor. Melexis sells a chip,
MLX10402, to Lego to do this job. Ask Melexis for a sample thu their web
site. Hope this helps.
Chuck >>
project. Is there a digital potentiometer which can do this or do I need to
use a separate chip for each one?
thanks
bob
[noparse][[/noparse]Non-text portions of this message have been removed]
The DS1806 has 6 pots on one chip but only has 64 tap positions. I you
don't need a high resolution pot that would be a great chip to use I doesn't
have NV Ram so you would have to store you tap position to your stamps
ram.Here is the link to the product table
hope this helps
Jason
Original Message
From: <eclecticrr@A...>
To: <basicstamps@yahoogroups.com>
Sent: Saturday, May 17, 2003 10:29 AM
Subject: [noparse][[/noparse]basicstamps] digital potentiometers
> I need to adjust the resistance of a lot of different circuits for a stamp
> project. Is there a digital potentiometer which can do this or do I need
to
> use a separate chip for each one?
>
> thanks
>
> bob
>
>
> [noparse][[/noparse]Non-text portions of this message have been removed]
>
>
> To UNSUBSCRIBE, just send mail to:
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Body of the message will be ignored.
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