Magnetic Coil
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Posts: 46,084
I am working on a project that involves turning on a magnetic coil
for brief periods (about 1 second, every 1 minute). The coil should
draw 2-4A at 6V. Can anyone recommend a common transistor that
would enable me to control this device with the BS2? It would also
help to know what other components need to be built into the circuit
to prevent damage to the stamp. I am a beginner as BS users go.
Any help would be appreciated.
Thanks,
Jack Miller
for brief periods (about 1 second, every 1 minute). The coil should
draw 2-4A at 6V. Can anyone recommend a common transistor that
would enable me to control this device with the BS2? It would also
help to know what other components need to be built into the circuit
to prevent damage to the stamp. I am a beginner as BS users go.
Any help would be appreciated.
Thanks,
Jack Miller
Comments
newsgroup about driving relays.
Is the 2-4A a varying load?, or are you not sure what the actual demand
from the coil is? If so, use Ohms law (I = V/R) where R is the coil
resistance and V = 6V to determine the current.
Select your transistor based on your current requirement X2 as a good
rule of thumb. Don't forget a diode in reverse bias across your coil
or transistor (E-C junction) to protect against back EMF from the coil.
>I am working on a project that involves turning on a magnetic coil
>for brief periods (about 1 second, every 1 minute). The coil should
>draw 2-4A at 6V. Can anyone recommend a common transistor that
>would enable me to control this device with the BS2? It would also
>help to know what other components need to be built into the circuit
>to prevent damage to the stamp. I am a beginner as BS users go.
>Any help would be appreciated.
>
>Thanks,
>
>Jack Miller
coils normally have a low inductance), you can not treated as a relay.
You can not turn a coil with DC, you have to drive the coil with a
very short duty cycle or some sort of alternating voltage not
necessarily a sinewave but a square wave.
relay.
Dennis
Original Message
From: jlmillerncsu [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=RNkJusTe0Ix43axdEdpZ0AwgK1vQNkPtCbKNTUFaGylmQbYV_6VQgrDdCvmkU9Ch1CNjSGRnAg]jmiller@n...[/url
Sent: Tuesday, December 09, 2003 10:33 AM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Magnetic Coil
I am working on a project that involves turning on a magnetic coil
for brief periods (about 1 second, every 1 minute). The coil should
draw 2-4A at 6V. Can anyone recommend a common transistor that
would enable me to control this device with the BS2? It would also
help to know what other components need to be built into the circuit
to prevent damage to the stamp. I am a beginner as BS users go.
Any help would be appreciated.
Thanks,
Jack Miller
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stamp.
http://www.geocities.com/jimforkin2003/
jim
Original Message
From: Beau Schwabe [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=RP-Hd-0jnAy0H8i9m3B4blO3809xkJuR3q5hTjY5geqrCM_uBSD6X15fghUjFm49otFk-lpyYOcHfl61BhYgQre6]bschwabe@a...[/url
Sent: Tuesday, December 09, 2003 2:32 PM
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] Magnetic Coil
Treat the coil as if it were a relay - there are several posts in this
newsgroup about driving relays.
Is the 2-4A a varying load?, or are you not sure what the actual demand
from the coil is? If so, use Ohms law (I = V/R) where R is the coil
resistance and V = 6V to determine the current.
Select your transistor based on your current requirement X2 as a good
rule of thumb. Don't forget a diode in reverse bias across your coil
or transistor (E-C junction) to protect against back EMF from the coil.
>I am working on a project that involves turning on a magnetic coil
>for brief periods (about 1 second, every 1 minute). The coil should
>draw 2-4A at 6V. Can anyone recommend a common transistor that
>would enable me to control this device with the BS2? It would also
>help to know what other components need to be built into the circuit
>to prevent damage to the stamp. I am a beginner as BS users go.
>Any help would be appreciated.
>
>Thanks,
>
>Jack Miller
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
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Body of the message will be ignored.
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Thanks for the reply. The load does not vary; I just have not
finalized the design of the coil. For the application, I need a
holding force of about 2 oz. My initial crude experiment used 24 ga
mag wire around a nail and had about the right degree of grab. The
problem was that this configuration had a resistance of about .4
ohm. I am planning to rework device using more turns and 30 ga
wire. I had estimated that I could get the current draw down to the
2 - 4A range and still maintain the holding force. I am also
looking for a source for a standard core of about 1/16 inch if
anyone knows of such a beast (so that I can abandon the nail
approach).
Jack
--- In basicstamps@yahoogroups.com, "Beau Schwabe" <bschwabe@a...>
wrote:
> Treat the coil as if it were a relay - there are several posts in
this
> newsgroup about driving relays.
>
> Is the 2-4A a varying load?, or are you not sure what the actual
demand
> from the coil is? If so, use Ohms law (I = V/R) where R is the
coil
> resistance and V = 6V to determine the current.
>
> Select your transistor based on your current requirement X2 as a
good
> rule of thumb. Don't forget a diode in reverse bias across your
coil
> or transistor (E-C junction) to protect against back EMF from the
coil.
>
> >I am working on a project that involves turning on a magnetic coil
> >for brief periods (about 1 second, every 1 minute). The coil
should
> >draw 2-4A at 6V. Can anyone recommend a common transistor that
> >would enable me to control this device with the BS2? It would
also
> >help to know what other components need to be built into the
circuit
> >to prevent damage to the stamp. I am a beginner as BS users go.
> >Any help would be appreciated.
> >
> >Thanks,
> >
> >Jack Miller
supply?
--- In basicstamps@yahoogroups.com, "Albert Catano"
<acatano2002@y...> wrote:
> First of all what is the inductance? If it has a air core (air
core
> coils normally have a low inductance), you can not treated as a
relay.
> You can not turn a coil with DC, you have to drive the coil with a
> very short duty cycle or some sort of alternating voltage not
> necessarily a sinewave but a square wave.
turned on with a TTL level, but wont support 4 amps. Id use a IRF511
Vmos FET. It has the back emf diode inside for keeping your bs2 from
blowing.
Chris Schur
--- In basicstamps@yahoogroups.com, "jlmillerncsu" <jmiller@n...>
wrote:
> I am working on a project that involves turning on a magnetic coil
> for brief periods (about 1 second, every 1 minute). The coil
should
> draw 2-4A at 6V. Can anyone recommend a common transistor that
> would enable me to control this device with the BS2? It would also
> help to know what other components need to be built into the
circuit
> to prevent damage to the stamp. I am a beginner as BS users go.
> Any help would be appreciated.
>
> Thanks,
>
> Jack Miller