transistor not triggering relay
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I have a DS2E-SL2-DC5V relay and a 2N7000 transistor. This is a DPDT
latching relay with coils rated at 5V DC, 35.9 mA. I manually
connected the relay to the 5V DC supply of the Basic Stamp 2 BOE to
test it and it works fine (switches an LED on and off). The problem
that I'm having is that the relay doesn't trigger when I use the
2N7000 transistor. I connected the source pin to ground, the gate pin
to pin 4 of the Basic Stamp and the drain pin to the coil. My Basic
Stamp program simply sets pin 4 high and then low with the desired
result to drive the transistor to trigger the relay. I'm concerned
that I may not have the correct transistor. I am a rookie so I don't
have a lot of test equipment (or knowledge of transistors). I need to
make sure that the transistor is will generate 5V DC at 35.9 mA or
better. Any help is appreciated.
latching relay with coils rated at 5V DC, 35.9 mA. I manually
connected the relay to the 5V DC supply of the Basic Stamp 2 BOE to
test it and it works fine (switches an LED on and off). The problem
that I'm having is that the relay doesn't trigger when I use the
2N7000 transistor. I connected the source pin to ground, the gate pin
to pin 4 of the Basic Stamp and the drain pin to the coil. My Basic
Stamp program simply sets pin 4 high and then low with the desired
result to drive the transistor to trigger the relay. I'm concerned
that I may not have the correct transistor. I am a rookie so I don't
have a lot of test equipment (or knowledge of transistors). I need to
make sure that the transistor is will generate 5V DC at 35.9 mA or
better. Any help is appreciated.
Comments
> I have a DS2E-SL2-DC5V relay and a 2N7000 transistor. This is a
DPDT
> latching relay with coils rated at 5V DC, 35.9 mA. I manually
> connected the relay to the 5V DC supply of the Basic Stamp 2 BOE to
> test it and it works fine (switches an LED on and off). The problem
> that I'm having is that the relay doesn't trigger when I use the
> 2N7000 transistor. I connected the source pin to ground, the gate
pin
> to pin 4 of the Basic Stamp and the drain pin to the coil. My Basic
> Stamp program simply sets pin 4 high and then low with the desired
> result to drive the transistor to trigger the relay. I'm concerned
> that I may not have the correct transistor. I am a rookie so I
don't
> have a lot of test equipment (or knowledge of transistors). I need
to
> make sure that the transistor is will generate 5V DC at 35.9 mA or
> better. Any help is appreciated.
Ok, I am not that experienced to answer this question and I know that
people that read this can answer it but I'll give it a shot. You are
using a mosfet transistor when you don't need to. I personally don't
use them, I use either pnp or npn transistor. You didn't mention a
resistor anywhere in the message which could be one problem but also
you have the source to ground and you are activating it with a low,
they are the same potential, so you won't be able to turn it on. Try
this, if you have one or get one at radio shack, get a 2n4401-it's a
npn. Then, connect the base to p4 but be sure to put like a 5k
resistor inline. Connect the emitter directly to ground and the
collector to your relay. This transistor will put out about 130ma,
more than you need. I hope this helps.
mosfets you need to have a gate to source voltage of around 10 volts before the
mosfet will be fully on. In your case I am thinking that perhaps the mosfet
isn't being driven correctly (5volts) so full conduction is not achieved
resulting in insufficient current flowing through the relay coil. Try using an
NPN transistor and keep your current configuration except note that
emitter = source
base = gate
collector = drain
Also make sure that you have a 10k resistor in series with pin 4 going to the
base of the NPN transistor. Another very popular transistor is the 2n2222A which
is sold at radio shack in quantities of 1 for .99cents
Good Luck!
-=Randy Knutson
christopher41877 wrote:--- In basicstamps@y..., "southernpost" wrote:
> I have a DS2E-SL2-DC5V relay and a 2N7000 transistor. This is a
DPDT
> latching relay with coils rated at 5V DC, 35.9 mA. I manually
> connected the relay to the 5V DC supply of the Basic Stamp 2 BOE to
> test it and it works fine (switches an LED on and off). The problem
> that I'm having is that the relay doesn't trigger when I use the
> 2N7000 transistor. I connected the source pin to ground, the gate
pin
> to pin 4 of the Basic Stamp and the drain pin to the coil. My Basic
> Stamp program simply sets pin 4 high and then low with the desired
> result to drive the transistor to trigger the relay. I'm concerned
> that I may not have the correct transistor. I am a rookie so I
don't
> have a lot of test equipment (or knowledge of transistors). I need
to
> make sure that the transistor is will generate 5V DC at 35.9 mA or
> better. Any help is appreciated.
Ok, I am not that experienced to answer this question and I know that
people that read this can answer it but I'll give it a shot. You are
using a mosfet transistor when you don't need to. I personally don't
use them, I use either pnp or npn transistor. You didn't mention a
resistor anywhere in the message which could be one problem but also
you have the source to ground and you are activating it with a low,
they are the same potential, so you won't be able to turn it on. Try
this, if you have one or get one at radio shack, get a 2n4401-it's a
npn. Then, connect the base to p4 but be sure to put like a 5k
resistor inline. Connect the emitter directly to ground and the
collector to your relay. This transistor will put out about 130ma,
more than you need. I hope this helps.
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[noparse][[/noparse]Non-text portions of this message have been removed]
MOSFET. I have used these in the past to control LED's and relay's.
You need a snubber diode across the coil of the relay. If you don't
have one you may have smoked the MOSFET. Connect cathode of diode to
side of coil that is connected to +5V. Connect anode to other side of
coil. For a diode use a 1N4004. Use a 10k ohm in series with the
gate.
Jason
--- In basicstamps@y..., Randy Knutson <ken_ryder@y...> wrote:
>
> I'm not sure on the specifics of that particular mosfet but to
drive many mosfets you need to have a gate to source voltage of
around 10 volts before the mosfet will be fully on. In your case I am
thinking that perhaps the mosfet isn't being driven correctly
(5volts) so full conduction is not achieved resulting in insufficient
current flowing through the relay coil. Try using an NPN transistor
and keep your current configuration except note that
> emitter = source
> base = gate
> collector = drain
> Also make sure that you have a 10k resistor in series with pin 4
going to the base of the NPN transistor. Another very popular
transistor is the 2n2222A which is sold at radio shack in quantities
of 1 for .99cents
> Good Luck!
> -=Randy Knutson
> christopher41877 wrote:--- In basicstamps@y..., "southernpost"
wrote:
> > I have a DS2E-SL2-DC5V relay and a 2N7000 transistor. This is a
> DPDT
> > latching relay with coils rated at 5V DC, 35.9 mA. I manually
> > connected the relay to the 5V DC supply of the Basic Stamp 2 BOE
to
> > test it and it works fine (switches an LED on and off). The
problem
> > that I'm having is that the relay doesn't trigger when I use the
> > 2N7000 transistor. I connected the source pin to ground, the gate
> pin
> > to pin 4 of the Basic Stamp and the drain pin to the coil. My
Basic
> > Stamp program simply sets pin 4 high and then low with the
desired
> > result to drive the transistor to trigger the relay. I'm
concerned
> > that I may not have the correct transistor. I am a rookie so I
> don't
> > have a lot of test equipment (or knowledge of transistors). I
need
> to
> > make sure that the transistor is will generate 5V DC at 35.9 mA
or
> > better. Any help is appreciated.
>
> Ok, I am not that experienced to answer this question and I know
that
> people that read this can answer it but I'll give it a shot. You
are
> using a mosfet transistor when you don't need to. I personally
don't
> use them, I use either pnp or npn transistor. You didn't mention a
> resistor anywhere in the message which could be one problem but
also
> you have the source to ground and you are activating it with a low,
> they are the same potential, so you won't be able to turn it on.
Try
> this, if you have one or get one at radio shack, get a 2n4401-it's
a
> npn. Then, connect the base to p4 but be sure to put like a 5k
> resistor inline. Connect the emitter directly to ground and the
> collector to your relay. This transistor will put out about 130ma,
> more than you need. I hope this helps.
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@y...
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Subject and Body of the message will be ignored.
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>
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>
>
>
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>
> [noparse][[/noparse]Non-text portions of this message have been removed]
application, however, you are not applying it correctly. Connect +5v to one
side of coil in relay, the other side of the coil to D on the mosfet. S to
ground (same as basic stamp) and the gate to the control pin though a 10K
resistor. The threshold voltage for this mosfet is only .8v. (this is the
point where the device starts to turn on) so you must go below this level on
G to turn off. You may not have ground referenced to vss on the stamp or
you may have enough noise on the control to have above .8volts on the gate.
If so, you may need an additional resistor (10k) to ground from the control
pin. It is also good practice to put a diode across the relay contacts
(cathode to +5vdc) to protect against counter-emf.
Good luck,
Jim
Original Message
From: Randy Knutson [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=ogUTWpw2ZObL1FJtXd9dKQGiiKz4Qre2MTOvzucLFIB7OWOBcigECYpmUmk7UykgjzpEXluwe7xMhj0]ken_ryder@y...[/url
Sent: Tuesday, August 27, 2002 5:26 PM
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] Re: transistor not triggering relay
I'm not sure on the specifics of that particular mosfet but to drive many
mosfets you need to have a gate to source voltage of around 10 volts before
the mosfet will be fully on. In your case I am thinking that perhaps the
mosfet isn't being driven correctly (5volts) so full conduction is not
achieved resulting in insufficient current flowing through the relay coil.
Try using an NPN transistor and keep your current configuration except note
that
emitter = source
base = gate
collector = drain
Also make sure that you have a 10k resistor in series with pin 4 going to
the base of the NPN transistor. Another very popular transistor is the
2n2222A which is sold at radio shack in quantities of 1 for .99cents
Good Luck!
-=Randy Knutson
christopher41877 wrote:--- In basicstamps@y..., "southernpost" wrote:
> I have a DS2E-SL2-DC5V relay and a 2N7000 transistor. This is a
DPDT
> latching relay with coils rated at 5V DC, 35.9 mA. I manually
> connected the relay to the 5V DC supply of the Basic Stamp 2 BOE to
> test it and it works fine (switches an LED on and off). The problem
> that I'm having is that the relay doesn't trigger when I use the
> 2N7000 transistor. I connected the source pin to ground, the gate
pin
> to pin 4 of the Basic Stamp and the drain pin to the coil. My Basic
> Stamp program simply sets pin 4 high and then low with the desired
> result to drive the transistor to trigger the relay. I'm concerned
> that I may not have the correct transistor. I am a rookie so I
don't
> have a lot of test equipment (or knowledge of transistors). I need
to
> make sure that the transistor is will generate 5V DC at 35.9 mA or
> better. Any help is appreciated.
Ok, I am not that experienced to answer this question and I know that
people that read this can answer it but I'll give it a shot. You are
using a mosfet transistor when you don't need to. I personally don't
use them, I use either pnp or npn transistor. You didn't mention a
resistor anywhere in the message which could be one problem but also
you have the source to ground and you are activating it with a low,
they are the same potential, so you won't be able to turn it on. Try
this, if you have one or get one at radio shack, get a 2n4401-it's a
npn. Then, connect the base to p4 but be sure to put like a 5k
resistor inline. Connect the emitter directly to ground and the
collector to your relay. This transistor will put out about 130ma,
more than you need. I hope this helps.
To UNSUBSCRIBE, just send mail to:
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Body of the message will be ignored.
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[noparse][[/noparse]Non-text portions of this message have been removed]
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