running multiple relay''s from BS-1
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Posts: 46,084
In 'normal' use (while the relay is activated)
the diode across the relay coil
should be reverse-biased (Cathode to +5, Anode to
the Stamp).
The purpose of the diode is that when you release
the coil, there is a current flowing, maintaining
a magnetic field, that is holding the contacts
closed. When you switch off the coil,
the magnetic field collapses. This generates
additional current in the coil which wants to go
somewhere. The diode gives it a place to go.
Without the diode, the current can only go into your
relay-driver circuitry -- which tends to burn it out.
Some Darlington transistor IC's have built-in
diodes for this purpose.
If you 'forward bias' the capacitor (Anode to +5,
cathode to the Stamp) then only 0.7 volts will be
across the coil, and it probably won't work.
--- In basicstamps@yahoogroups.com, "Brent" <haksaw@r...> wrote:
> Thank you,
>
> I do have enough output pins and this looks like the method to use
> since on this project I will also need to switch different
> voltages. I like Sid's advice and can think of even more projets
> now that I can get more outputs from teh BS-1 cool....
>
> I do have another qurestion for you, you mention in you additional
> note that I should put a diode across the relay? do you mean from
> the + to the - side of the relay? can you please explain to me why
> this is needed (I don't want to screw anything up and would like to
> understand the purpose of all component, for future refference)
>
> thank you all again
> Brent
> HAKSAW_CA
>
>
> --- In basicstamps@yahoogroups.com, smartdim@a... wrote:
> > If you have 4 available output pins go to the files section of
> www.yahoogroups.com, Basic Stamps group, and look for the file
named
> IRL520.jpg
> >
> > This is only one of many methods that will work. Sid mentioned
> using a '595 shift register and a Darlington array, and that
> solution also works and if memory serves me correctly, it the '595
> will consume 3 stamp pins.
> >
> > The IRL520 method is a simple way to drive your relay coils. A
> logic high from the stamp will engergize the relay coil......so
> unless you are tight on available output pins, the IRL520 mosfets
> will do the job.
> >
> > A good source and inexpensive shipping for the IRL's is
> www.glitchbuster.com (and I am not affiliated with them in any way,
> just a happy customer).
> >
> > Additional note. Be sure to place a diode across the relay coil,
> cathode (end with a stripe) to the positive side of the relay coil
the diode across the relay coil
should be reverse-biased (Cathode to +5, Anode to
the Stamp).
The purpose of the diode is that when you release
the coil, there is a current flowing, maintaining
a magnetic field, that is holding the contacts
closed. When you switch off the coil,
the magnetic field collapses. This generates
additional current in the coil which wants to go
somewhere. The diode gives it a place to go.
Without the diode, the current can only go into your
relay-driver circuitry -- which tends to burn it out.
Some Darlington transistor IC's have built-in
diodes for this purpose.
If you 'forward bias' the capacitor (Anode to +5,
cathode to the Stamp) then only 0.7 volts will be
across the coil, and it probably won't work.
--- In basicstamps@yahoogroups.com, "Brent" <haksaw@r...> wrote:
> Thank you,
>
> I do have enough output pins and this looks like the method to use
> since on this project I will also need to switch different
> voltages. I like Sid's advice and can think of even more projets
> now that I can get more outputs from teh BS-1 cool....
>
> I do have another qurestion for you, you mention in you additional
> note that I should put a diode across the relay? do you mean from
> the + to the - side of the relay? can you please explain to me why
> this is needed (I don't want to screw anything up and would like to
> understand the purpose of all component, for future refference)
>
> thank you all again
> Brent
> HAKSAW_CA
>
>
> --- In basicstamps@yahoogroups.com, smartdim@a... wrote:
> > If you have 4 available output pins go to the files section of
> www.yahoogroups.com, Basic Stamps group, and look for the file
named
> IRL520.jpg
> >
> > This is only one of many methods that will work. Sid mentioned
> using a '595 shift register and a Darlington array, and that
> solution also works and if memory serves me correctly, it the '595
> will consume 3 stamp pins.
> >
> > The IRL520 method is a simple way to drive your relay coils. A
> logic high from the stamp will engergize the relay coil......so
> unless you are tight on available output pins, the IRL520 mosfets
> will do the job.
> >
> > A good source and inexpensive shipping for the IRL's is
> www.glitchbuster.com (and I am not affiliated with them in any way,
> just a happy customer).
> >
> > Additional note. Be sure to place a diode across the relay coil,
> cathode (end with a stripe) to the positive side of the relay coil