Latching relay - was Re: Most reliable relay?
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I'm using a NO solid-state SPST relay to turn ON/OFF 2 steppers. But it
sometimes latches and won't obey a Stamp command to turn off. The relay
current & voltage ratings are appropriate for the steppers, and I'm
using a ULN2003 Darlington as a relay driver.
Should I go for a larger-amp relay, or could I add another component
such as a diode or cap to prevent this?
Dennis
Original Message
From: Dave Mucha <davemucha@j...> [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=4zJ1Flo7Z8xb3q3v7HT22TmZsMV0OMu6M_m6lw7RWt9ExxL9_Md0cDaORpHIzY4L-Gw-DDInAU4L]davemucha@j...[/url
Sent: Saturday, December 28, 2002 4:18 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Re: Most reliable relay?
most reliable relay ?
any name brand unit. get one that is low coil wattage so you are not
heating it up too much, power it for the proper voltage and current
rating.
Life of coils is measured in number of closures, not life of coil, so
your infrequent coil closure is not going to effect the life.
The relay Sid listed is small, very unobtrusive and has a closure
rating of like a million closures. Hard to beat that.
Also, the minature unit will have a low power drain meaning low
heat. also good for longer life.
Dave
sometimes latches and won't obey a Stamp command to turn off. The relay
current & voltage ratings are appropriate for the steppers, and I'm
using a ULN2003 Darlington as a relay driver.
Should I go for a larger-amp relay, or could I add another component
such as a diode or cap to prevent this?
Dennis
Original Message
From: Dave Mucha <davemucha@j...> [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=4zJ1Flo7Z8xb3q3v7HT22TmZsMV0OMu6M_m6lw7RWt9ExxL9_Md0cDaORpHIzY4L-Gw-DDInAU4L]davemucha@j...[/url
Sent: Saturday, December 28, 2002 4:18 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Re: Most reliable relay?
most reliable relay ?
any name brand unit. get one that is low coil wattage so you are not
heating it up too much, power it for the proper voltage and current
rating.
Life of coils is measured in number of closures, not life of coil, so
your infrequent coil closure is not going to effect the life.
The relay Sid listed is small, very unobtrusive and has a closure
rating of like a million closures. Hard to beat that.
Also, the minature unit will have a low power drain meaning low
heat. also good for longer life.
Dave
Comments
Original Message
From: "Dennis P. O'Leary" <doleary@e...>
To: <basicstamps@yahoogroups.com>
Sent: Saturday, December 28, 2002 9:29 PM
Subject: RE: [noparse][[/noparse]basicstamps] Latching relay - was Re: Most reliable relay?
> I'm using a NO solid-state SPST relay to turn ON/OFF 2 steppers. But it
> sometimes latches and won't obey a Stamp command to turn off. The relay
> current & voltage ratings are appropriate for the steppers, and I'm
> using a ULN2003 Darlington as a relay driver.
>
> Should I go for a larger-amp relay, or could I add another component
> such as a diode or cap to prevent this?
*******************************************
Hi Dennis;
Some thoughts come to mind: If the SS relay uses a transistor, and the
inductive spike from the stepper coils induce transistor breakdown at
turn-off, the relay could "latch". This would be solved with a catch diode
on the stepper coils. I don't know your setup, so this may not be
applicable.
Ray McArthur
solution, which is also supported in Horowitz & Hill, page 52.
Dennis
Original Message
From: Ray McArthur [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=hOgmC_bOEdk7sOnIZuTekvLA_bUKcmPwfxR-L6iiFpDAd1knT7wCdW5mrMAPdsfuC3GXMU0mBAswPUA4hF-4]rjmca@u...[/url
Sent: Saturday, December 28, 2002 7:43 PM
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] Latching relay - was Re: Most reliable relay?
Hi Dennis;
Some thoughts come to mind: If the SS relay uses a transistor, and the
inductive spike from the stepper coils induce transistor breakdown at
turn-off, the relay could "latch". This would be solved with a catch
diode on the stepper coils. I don't know your setup, so this may not be
applicable.
Ray McArthur