attaching a relay on an output pin - basics
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Posts: 46,084
--- In basicstamps@yahoogroups.com, "jeff_alten" <jeffalten@h...>
wrote:
> Hi, I'm trying to attach a 6vdc trigger industrial strength coil
> relay to an output on my basic stamp 2. It is being used to control
> the on/off of a 110 volts, 6 amps ac motor. But right now i'm just
> stuck at making sure the relay works. I'v tested the relay that I
> was planning to use and it works fine with a manual switch. But
when
> I hooked it up to the stamp it won't switch states. The led
attached
> to the same output is going from low to high, but the relay is not
> following, it is getting power it's just not being triggered. I
> don't know what I'm missing? I would appreaciate any and all
> suggestions...Oh and I did have it hooked up to an opto isolater
4n32
> but it didn't work so I began to strip it down and now I'm just as
> confused as ever.
>
> thanks jeff
Hi Jeff,
coil resistance. coil voltage. ohm's law.
determine the current you need to drive it.
chances are a 2N2222 or similar trasnsistor will handle the load to
drive the coil.
the Stamp can handle driving the 2222.
The Base of the transistor is the driving pin. On an NPN, the
collector is where you connect the ground of the relay to the
transistor. The plus of the relay is connected direct to the power
supply.
the transistor can pass a current that has a relationship to the base
current.
an example is a 50! current. so 1mA on the base = 50mA on the
transistor if the transistor is rated for 50mA. if you saturate the
base, you guarantee you have turned the transistor on fully.
so what if you need 500mA and the transistor is rated for that ? it
would need 10mA, if you used one transistor that drove the base of
the second, you would multiply the first base signal by 50.
maybe a poor way to describe a darlington pair of transistors, but
the idea is a small input yields a large output.
A '03 chip (2803,2003) has an internal diode to protect from the
relay opening and creating a spike. the TIP120 darlington, single
channel, TO220 package, higher amps, also has an internal diode.
The relay coil is an indcutor so it will resist the intput change and
will spike the output when the circuit opens. you need to protect
from that, so the diode is included in many chips like the ULN2003,
or TIP120. the 2N222 will need an external diode if you use that.
Dave
wrote:
> Hi, I'm trying to attach a 6vdc trigger industrial strength coil
> relay to an output on my basic stamp 2. It is being used to control
> the on/off of a 110 volts, 6 amps ac motor. But right now i'm just
> stuck at making sure the relay works. I'v tested the relay that I
> was planning to use and it works fine with a manual switch. But
when
> I hooked it up to the stamp it won't switch states. The led
attached
> to the same output is going from low to high, but the relay is not
> following, it is getting power it's just not being triggered. I
> don't know what I'm missing? I would appreaciate any and all
> suggestions...Oh and I did have it hooked up to an opto isolater
4n32
> but it didn't work so I began to strip it down and now I'm just as
> confused as ever.
>
> thanks jeff
Hi Jeff,
coil resistance. coil voltage. ohm's law.
determine the current you need to drive it.
chances are a 2N2222 or similar trasnsistor will handle the load to
drive the coil.
the Stamp can handle driving the 2222.
The Base of the transistor is the driving pin. On an NPN, the
collector is where you connect the ground of the relay to the
transistor. The plus of the relay is connected direct to the power
supply.
the transistor can pass a current that has a relationship to the base
current.
an example is a 50! current. so 1mA on the base = 50mA on the
transistor if the transistor is rated for 50mA. if you saturate the
base, you guarantee you have turned the transistor on fully.
so what if you need 500mA and the transistor is rated for that ? it
would need 10mA, if you used one transistor that drove the base of
the second, you would multiply the first base signal by 50.
maybe a poor way to describe a darlington pair of transistors, but
the idea is a small input yields a large output.
A '03 chip (2803,2003) has an internal diode to protect from the
relay opening and creating a spike. the TIP120 darlington, single
channel, TO220 package, higher amps, also has an internal diode.
The relay coil is an indcutor so it will resist the intput change and
will spike the output when the circuit opens. you need to protect
from that, so the diode is included in many chips like the ULN2003,
or TIP120. the 2N222 will need an external diode if you use that.
Dave
Comments
like a charm.
thanks to all again.
jeff
>From: "Dave Mucha" <davemucha@j...>
>Reply-To: basicstamps@yahoogroups.com
>To: basicstamps@yahoogroups.com
>Subject: [noparse][[/noparse]basicstamps] Re: attaching a relay on an output pin - basics
>Date: Wed, 26 Nov 2003 21:07:07 -0000
>
>--- In basicstamps@yahoogroups.com, "jeff_alten" <jeffalten@h...>
>wrote:
> > Hi, I'm trying to attach a 6vdc trigger industrial strength coil
> > relay to an output on my basic stamp 2. It is being used to control
> > the on/off of a 110 volts, 6 amps ac motor. But right now i'm just
> > stuck at making sure the relay works. I'v tested the relay that I
> > was planning to use and it works fine with a manual switch. But
>when
> > I hooked it up to the stamp it won't switch states. The led
>attached
> > to the same output is going from low to high, but the relay is not
> > following, it is getting power it's just not being triggered. I
> > don't know what I'm missing? I would appreaciate any and all
> > suggestions...Oh and I did have it hooked up to an opto isolater
>4n32
> > but it didn't work so I began to strip it down and now I'm just as
> > confused as ever.
> >
> > thanks jeff
>
>Hi Jeff,
>
>coil resistance. coil voltage. ohm's law.
>determine the current you need to drive it.
>
>chances are a 2N2222 or similar trasnsistor will handle the load to
>drive the coil.
>
>the Stamp can handle driving the 2222.
>
>The Base of the transistor is the driving pin. On an NPN, the
>collector is where you connect the ground of the relay to the
>transistor. The plus of the relay is connected direct to the power
>supply.
>
>the transistor can pass a current that has a relationship to the base
>current.
>
>an example is a 50! current. so 1mA on the base = 50mA on the
>transistor if the transistor is rated for 50mA. if you saturate the
>base, you guarantee you have turned the transistor on fully.
>
>so what if you need 500mA and the transistor is rated for that ? it
>would need 10mA, if you used one transistor that drove the base of
>the second, you would multiply the first base signal by 50.
>
>maybe a poor way to describe a darlington pair of transistors, but
>the idea is a small input yields a large output.
>
>A '03 chip (2803,2003) has an internal diode to protect from the
>relay opening and creating a spike. the TIP120 darlington, single
>channel, TO220 package, higher amps, also has an internal diode.
>
>The relay coil is an indcutor so it will resist the intput change and
>will spike the output when the circuit opens. you need to protect
>from that, so the diode is included in many chips like the ULN2003,
>or TIP120. the 2N222 will need an external diode if you use that.
>
>
>Dave
>
>
>
>
>
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