Circuit for 0-1 amp variable current
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Posts: 46,084
Hi
I have a proportional valve that requires variable current to operate. At
approximately 800 mA the valve is fully open. It is proportional from approx
0 amps to 800 mA. I want to drive the valve with a pic or stamp.
Can anyone recommend a circuit that a pic or stamp can drive which can output
that range of variable current?
Maybe PWM at a high frequency?
Any help would be great.
Thanks
Jon
I have a proportional valve that requires variable current to operate. At
approximately 800 mA the valve is fully open. It is proportional from approx
0 amps to 800 mA. I want to drive the valve with a pic or stamp.
Can anyone recommend a circuit that a pic or stamp can drive which can output
that range of variable current?
Maybe PWM at a high frequency?
Any help would be great.
Thanks
Jon
Comments
>Hi
>
>I have a proportional valve that requires variable current to operate. At
>approximately 800 mA the valve is fully open. It is proportional from approx
>0 amps to 800 mA. I want to drive the valve with a pic or stamp.
>
>Can anyone recommend a circuit that a pic or stamp can drive which can
output
>that range of variable current?
>
>Maybe PWM at a high frequency?
>
>Any help would be great.
>
>Thanks
>
>Jon
Hi Jon -
There was an <ahem> seminar on the old stamp list on this very topic <g>.
I can probably strip it off my own Stamp List archives, and zip it
for you ???
I have NO idea what to tell you otherwise, since the off-site Stamp archive
is quite out-of-date, and I'm not exactly sure of the status of the Parallax
site, as regards archives.
Honestly - I haven't even looked at the new Parallax website, I'm sorry to
say;
too darned busy. Don't need to for archives when ya keep yer own, though <g>.
For you, the fee will be reasonable <grin>.
Lemme know whatch wanna do, kind sir.
Regards,
Bruce
>
>
>
>eGroups.com home: http://www.egroups.com/group/basicstamps
>http://www.egroups.com - Simplifying group communications
>
>
>
>
>
You might want to check the National Semiconductor data books or web site.
In App Note 31, there are many op-amp circuits including a current source
and sink. Also, take a look at the LM675 power op-amp. The data sheet for
this guy shows a high current source/sink. You could use the PWM output of
the Stamp w/filter to drive the op-amp of the current source/sink.
At 01:09 AM 30/3/00 -0500, you wrote:
>Hi
>
>I have a proportional valve that requires variable current to operate. At
>approximately 800 mA the valve is fully open. It is proportional from approx
>0 amps to 800 mA. I want to drive the valve with a pic or stamp.
>
>Can anyone recommend a circuit that a pic or stamp can drive which can output
>that range of variable current?
>
>Maybe PWM at a high frequency?
>
>Any help would be great.
>
>Thanks
>
>Jon
>
>
>
>eGroups.com home: http://www.egroups.com/group/basicstamps
>http://www.egroups.com - Simplifying group communications
>
>
>
>
258 Metals Development
Ames Laboratory
Iowa State University
>I have a proportional valve that requires variable current to operate. At
>approximately 800 mA the valve is fully open. It is proportional from
approx
>0 amps to 800 mA. I want to drive the valve with a pic or stamp.
>
>Can anyone recommend a circuit that a pic or stamp can drive which can
output
>that range of variable current?
Hi Jon,
Here is a classic voltage controlled current sink, 100% PWM at P0 gives
800ma to the valve.
Current proportional to %PWM.
;
o
+24 volts
| |
op-amp | |
LM358 | valve 0->800ma
|\| |
P0--/\/\-o--- |+\ |/----'
10k | | >--| NPN adequate power
| ;--|-/ |\>-; or mosfet
| | |/ |
| '
o
| |
1uf=== /
| \ 6.25 ohms, 5 watt
| /
| |
o
o----Vss
The stamp can come around once every few seconds to refresh the charge on
the PWM capacitor.
--Tracy Allen
Electronically Monitored Ecosystems
http://www.emesystems.com
Jon
In a message dated 3/30/00 12:41:10 PM US Mountain Standard Time,
harker@a... writes:
<< Jon,
You might want to check the National Semiconductor data books or web site.
In App Note 31, there are many op-amp circuits including a current source
and sink. Also, take a look at the LM675 power op-amp. The data sheet for
this guy shows a high current source/sink. You could use the PWM output of
the Stamp w/filter to drive the op-amp of the current source/sink >>
That sounds like a neat valve! Could you tell me the make, model and price
range?
Thanks,
Roger
At 02:59 PM 3/30/00 -0500, you wrote:
>Jon wrote:
>>I have a proportional valve that requires variable current to operate. At
>>approximately 800 mA the valve is fully open. It is proportional from
>approx
>>0 amps to 800 mA. I want to drive the valve with a pic or stamp.
>>
>>Can anyone recommend a circuit that a pic or stamp can drive which can
>output
>>that range of variable current?
>
>Hi Jon,
>
>Here is a classic voltage controlled current sink, 100% PWM at P0 gives
>800ma to the valve.
>Current proportional to %PWM.
>
> ;
o
+24 volts
> | |
> op-amp | |
> LM358 | valve 0->800ma
> |\| |
> P0--/\/\-o--- |+\ |/----'
> 10k | | >--| NPN adequate power
> | ;--|-/ |\>-; or mosfet
> | | |/ |
> | '
o
> | |
> 1uf=== /
> | \ 6.25 ohms, 5 watt
> | /
> | |
>
o
o----Vss
>
>The stamp can come around once every few seconds to refresh the charge on
>the PWM capacitor.
>
> --Tracy Allen
> Electronically Monitored Ecosystems
> http://www.emesystems.com
>
>
>
>eGroups.com home: http://www.egroups.com/group/basicstamps
>http://www.egroups.com - Simplifying group communications
>
>
>
>
>
>
Roger Edberg
rjedberg@c...
http://www.cruzio.com/~pgraphic
I am also interested in this valve. Can you tell me the orfice size along
with everything below.
Thanks
Derek Barger
>Hi Jon,
>That sounds like a neat valve! Could you tell me the make, model and price
>range?
>Thanks,
>Roger
>
>At 02:59 PM 3/30/00 -0500, you wrote:
>>Jon wrote:
>>>I have a proportional valve that requires variable current to operate. At
>>>approximately 800 mA the valve is fully open. It is proportional from
>>approx
>>>0 amps to 800 mA. I want to drive the valve with a pic or stamp.
>>>
>>>Can anyone recommend a circuit that a pic or stamp can drive which can
>>output
>>>that range of variable current?
>>
>>Hi Jon,
>>
>>Here is a classic voltage controlled current sink, 100% PWM at P0 gives
>>800ma to the valve.
>>Current proportional to %PWM.
>>
>> ;
o
+24 volts
>> | |
>> op-amp | |
>> LM358 | valve 0->800ma
>> |\| |
>> P0--/\/\-o--- |+\ |/----'
>> 10k | | >--| NPN adequate power
>> | ;--|-/ |\>-; or mosfet
>> | | |/ |
>> | '
o
>> | |
>> 1uf=== /
>> | \ 6.25 ohms, 5 watt
>> | /
>> | |
>>
o
o----Vss
>>
>>The stamp can come around once every few seconds to refresh the charge on
>>the PWM capacitor.
>>
>> --Tracy Allen
>> Electronically Monitored Ecosystems
>> http://www.emesystems.com
>>
>>
>>
>>eGroups.com home: http://www.egroups.com/group/basicstamps
>>http://www.egroups.com - Simplifying group communications
>>
>>
>>
>>
>>
>>
>
>Roger Edberg
>rjedberg@c...
>http://www.cruzio.com/~pgraphic
>
>
>
>eGroups.com home: http://www.egroups.com/group/basicstamps
>http://www.egroups.com - Simplifying group communications
>
>
>
>