OT: Clamping Diodes
Archiver
Posts: 46,084
Good Day Everyone,
This is off topic I know, but maybe others need to know too. I
need to put a clamping diode across a solenoid coil to protect the drive
electronics from the turn-off voltage spike. My question is: Can I use a
general purpose diode here, as long as conditions don't exceed the diodes
ratings? I'm thinking of the 1N4000 series. Or does this need to be a
fast recovery diode? Recommendations?
Thanks,
Tim
Timothy Medema
CrystaLite, Incorporated
3307 Cedar St. (425) 745-6000 800-666-6065
Everett, WA 98201 Fax: (425) 257-0232
www.crystaliteinc.com
<mailto:timm@c...>timm@c...
The information transmitted is intended only for the person or entity to
whom it is addressed and may contain confidential and/or privileged
material. Any review, retransmission, dissemination or other use of, or
taking of any action in reliance upon, this information by persons or
entities other than the intended recipient is prohibited. If you received
this in error, please contact the sender and delete the material from any
computer.
This is off topic I know, but maybe others need to know too. I
need to put a clamping diode across a solenoid coil to protect the drive
electronics from the turn-off voltage spike. My question is: Can I use a
general purpose diode here, as long as conditions don't exceed the diodes
ratings? I'm thinking of the 1N4000 series. Or does this need to be a
fast recovery diode? Recommendations?
Thanks,
Tim
Timothy Medema
CrystaLite, Incorporated
3307 Cedar St. (425) 745-6000 800-666-6065
Everett, WA 98201 Fax: (425) 257-0232
www.crystaliteinc.com
<mailto:timm@c...>timm@c...
The information transmitted is intended only for the person or entity to
whom it is addressed and may contain confidential and/or privileged
material. Any review, retransmission, dissemination or other use of, or
taking of any action in reliance upon, this information by persons or
entities other than the intended recipient is prohibited. If you received
this in error, please contact the sender and delete the material from any
computer.
Comments
Yes, need FR diode for voltage spikes.
Best regards,
Kalun mailto:klnlau@v...
Monday, October 07, 2002, 10:55:06 AM, you wrote:
TM> Good Day Everyone,
TM> This is off topic I know, but maybe others need to know too. I
TM> need to put a clamping diode across a solenoid coil to protect the drive
TM> electronics from the turn-off voltage spike. My question is: Can I use a
TM> general purpose diode here, as long as conditions don't exceed the diodes
TM> ratings? I'm thinking of the 1N4000 series. Or does this need to be a
TM> fast recovery diode? Recommendations?
TM> Thanks,
TM> Tim
TM> Timothy Medema
TM> CrystaLite, Incorporated
TM> 3307 Cedar St. (425) 745-6000 800-666-6065
TM> Everett, WA 98201 Fax: (425) 257-0232
TM> www.crystaliteinc.com
TM> <mailto:timm@c...>timm@c...
TM> The information transmitted is intended only for the person or entity to
TM> whom it is addressed and may contain confidential and/or privileged
TM> material. Any review, retransmission, dissemination or other use of, or
TM> taking of any action in reliance upon, this information by persons or
TM> entities other than the intended recipient is prohibited. If you received
TM> this in error, please contact the sender and delete the material from any
TM> computer.
TM> To UNSUBSCRIBE, just send mail to:
TM> basicstamps-unsubscribe@yahoogroups.com
TM> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
TM> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
[noparse][[/noparse]Non-text portions of this message have been removed]
Tim
At 11:48 AM 10/7/2002 -0500, you wrote:
>Hello Timothy,
>
>Yes, need FR diode for voltage spikes.
>
>Best regards,
> Kalun mailto:klnlau@v...
>
>
>Monday, October 07, 2002, 10:55:06 AM, you wrote:
>
>
>TM> Good Day Everyone,
>
>TM> This is off topic I know, but maybe others need to know too. I
>TM> need to put a clamping diode across a solenoid coil to protect the drive
>TM> electronics from the turn-off voltage spike. My question is: Can I use a
>TM> general purpose diode here, as long as conditions don't exceed the diodes
>TM> ratings? I'm thinking of the 1N4000 series. Or does this need to be a
>TM> fast recovery diode? Recommendations?
>
>TM> Thanks,
>
>TM> Tim
>
>
>TM> Timothy Medema
>TM> CrystaLite, Incorporated
>TM> 3307 Cedar St. (425) 745-6000 800-666-6065
>TM> Everett, WA 98201 Fax: (425) 257-0232
>
>TM> www.crystaliteinc.com
>TM> <mailto:timm@c...>timm@c...
>
>
>TM> The information transmitted is intended only for the person or entity to
>TM> whom it is addressed and may contain confidential and/or privileged
>TM> material. Any review, retransmission, dissemination or other use of, or
>TM> taking of any action in reliance upon, this information by persons or
>TM> entities other than the intended recipient is prohibited. If you
>received
>TM> this in error, please contact the sender and delete the material from any
>TM> computer.
>
>
>TM> To UNSUBSCRIBE, just send mail to:
>TM> basicstamps-unsubscribe@yahoogroups.com
>TM> from the same email address that you subscribed. Text in the Subject
>and Body of the message will be ignored.
>
>
>TM> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
>To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
>from the same email address that you subscribed. Text in the Subject and
>Body of the message will be ignored.
>
>
>Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
1n4000 series part across the relay! The only time you would need a fast
recovery diode would be in the case of a "high frequency" type of transformer
(ie. HV flyback transformer such as is used in TVs or CRTs or for a DC/DC
converters that uses higher frequencies. Since a relay is not a device that
is switched on and off very rapidly and since the inductance of the coil is
usually quite large, a simple "slow" type of rectifier is all that is needed!
The sole purpose of this diode is to kinock out the reverse polarity emf
generated by the inductance of the relay coil.
[noparse][[/noparse]Non-text portions of this message have been removed]
seeing as I have many of them on the shelf.
Tim
At 01:51 PM 10/7/2002 -0400, you wrote:
>If you open up and look at any piece of electronic equipment you will find a
>1n4000 series part across the relay! The only time you would need a fast
>recovery diode would be in the case of a "high frequency" type of transformer
>(ie. HV flyback transformer such as is used in TVs or CRTs or for a DC/DC
>converters that uses higher frequencies. Since a relay is not a device that
>is switched on and off very rapidly and since the inductance of the coil is
>usually quite large, a simple "slow" type of rectifier is all that is needed!
>The sole purpose of this diode is to kinock out the reverse polarity emf
>generated by the inductance of the relay coil.
>
>
>[noparse][[/noparse]Non-text portions of this message have been removed]
>
>
>To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
>from the same email address that you subscribed. Text in the Subject and
>Body of the message will be ignored.
>
>
>Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
Don't use a 1N4148 or 1N914, they will blow eventually. Believe it or not,
a friend had a Kodak slide projector that had failed - and the reason was
that the back emf diode was a 1N914!! I measured the back emf with an
Oscilloscope, and we were getting -500V! Replaced with a 1N4007 and no
trouble since (10 years ago).
--
http://www.lennard.net.nz/
Ben Lennard, NCEE, Dip EE
Electronics R&D
Hm: +64 4 972 7567
Mb: +64 21 536 627
87 Spencer Street
Crofton Downs
Wellington
New Zealand
"To the optimist, the glass is half full. To the pessimist, the glass is
half empty. To the engineer, the glass is twice as big as it needs to be."
No animals were harmed in the transmission of this email, although the
Dog next door is living on borrowed time, let me tell you! Those of you
with an overwhelming fear of the unknown will be gratified to learn that
there is no hidden message revealed by reading this warning backwards.
> From: azeasi@a...
> Reply-To: basicstamps@yahoogroups.com
> Date: Mon, 7 Oct 2002 13:42:06 EDT
> To: basicstamps@yahoogroups.com
> Subject: Re: [noparse][[/noparse]basicstamps] OT: Clamping Diodes
>
> Any diode (ie 1N4000 series is fine) for this purpose!
>
>
> [noparse][[/noparse]Non-text portions of this message have been removed]
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and Body
> of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
Original Message
From: "Timothy Medema" <timm@c...>
> Good Day Everyone,
>
> This is off topic I know, but maybe others need to know too. I
> need to put a clamping diode across a solenoid coil to protect the drive
> electronics from the turn-off voltage spike. My question is: Can I use a
> general purpose diode here, as long as conditions don't exceed the diodes
> ratings? I'm thinking of the 1N4000 series. Or does this need to be a
> fast recovery diode? Recommendations?
************
Choosing a clamp diode is straightforward:
The reverse voltage rating should be greater than your power supply, ie, if
it's a 12 volt relay, the diode should have a breakdown voltage greater than
12V, (easily met with most cheap diodes). The current rating should be
equal/greater than the coil current, since this current flows momentarily
through the diode. Diode recovery speed is not an issue here, so general
purpose diodes are fine.
Hope this helps,
Ray McArthur
The back emf created by a collasping magnetic field of a Relay or solenoid
is large (hundreds of volts), as in the example I mentioned before (where I
measured a -500V spike).
So, your clamping diode needs to withstand a few hundred volts, not just
have a reverse voltage greater than the voltage of the power supply. So a
1N4007 (1000v reverse voltage, 1A forward current), is the one to go for.
--
http://www.lennard.net.nz/
Ben Lennard, NCEE, Dip EE
Electronics R&D
Hm: +64 4 972 7567
Mb: +64 21 536 627
87 Spencer Street
Crofton Downs
Wellington
New Zealand
"To the optimist, the glass is half full. To the pessimist, the glass is
half empty. To the engineer, the glass is twice as big as it needs to be."
No animals were harmed in the transmission of this email, although the
Dog next door is living on borrowed time, let me tell you! Those of you
with an overwhelming fear of the unknown will be gratified to learn that
there is no hidden message revealed by reading this warning backwards.
> From: "Ray McArthur" <rjmca@u...>
> Reply-To: basicstamps@yahoogroups.com
> Date: Mon, 7 Oct 2002 21:29:39 -0400
> To: <basicstamps@yahoogroups.com>
> Subject: Re: [noparse][[/noparse]basicstamps] OT: Clamping Diodes
>
>
Original Message
> From: "Timothy Medema" <timm@c...>
>> Good Day Everyone,
>>
>> This is off topic I know, but maybe others need to know too. I
>> need to put a clamping diode across a solenoid coil to protect the drive
>> electronics from the turn-off voltage spike. My question is: Can I use a
>> general purpose diode here, as long as conditions don't exceed the diodes
>> ratings? I'm thinking of the 1N4000 series. Or does this need to be a
>> fast recovery diode? Recommendations?
> ************
> Choosing a clamp diode is straightforward:
> The reverse voltage rating should be greater than your power supply, ie, if
> it's a 12 volt relay, the diode should have a breakdown voltage greater than
> 12V, (easily met with most cheap diodes). The current rating should be
> equal/greater than the coil current, since this current flows momentarily
> through the diode. Diode recovery speed is not an issue here, so general
> purpose diodes are fine.
>
> Hope this helps,
> Ray McArthur
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and Body
> of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
Original Message
From: "Ben" <ben@l...>
> Not quiet right.
>
> The back emf created by a collasping magnetic field of a Relay or solenoid
> is large (hundreds of volts), as in the example I mentioned before (where
I
> measured a -500V spike).
>
> So, your clamping diode needs to withstand a few hundred volts, not just
> have a reverse voltage greater than the voltage of the power supply. So a
> 1N4007 (1000v reverse voltage, 1A forward current), is the one to go for.
>
*************************
Ben
The hundreds of volts you saw will not happen if the diode clamp is in
place. The spike happens if there is nowhere for the stored energy to go.
Regards,
Ray McArthur
[noparse][[/noparse]Non-text portions of this message have been removed]
>Not quiet right.
>
>The back emf created by a collasping magnetic field of a Relay or solenoid
>is large (hundreds of volts), as in the example I mentioned before (where I
>measured a -500V spike).
>
>So, your clamping diode needs to withstand a few hundred volts, not just
>have a reverse voltage greater than the voltage of the power supply. So a
>1N4007 (1000v reverse voltage, 1A forward current), is the one to go for.
Sorry - but this is NOT correct!
The diode is there to STOP that high voltage spike from occurring! The
maximum voltage across the diode is somewhat larger than the supply voltage
- that's all.
Draw it out and sketch the spike that occurs when the transistor turns
off. Now draw in the diode and look where the current goes when the spike
occurs. The diode is OFF during normal operation and conducts only when
the spike occurs.
I don't use small signal diodes (1n914, 1n4148) for clamping the back EMF
spikes on relay coil drivers because of CURRENT ratings, not voltage
ratings. Those small silicon diodes are good for about 75V but only a few
tens of mA. The diode has to handle the full coil current at the leading
edge of the spike and a 1n914 just isn't beefy enough.
dwayne
--
Dwayne Reid <dwayner@p...>
Trinity Electronics Systems Ltd Edmonton, AB, CANADA
(780) 489-3199 voice (780) 487-6397 fax
Celebrating 18 years of Engineering Innovation (1984 - 2002)
.-. .-. .-. .-. .-. .-. .-. .-. .-. .-
`-' `-' `-' `-' `-' `-' `-' `-' `-'
Do NOT send unsolicited commercial email to this email address.
This message neither grants consent to receive unsolicited
commercial email nor is intended to solicit commercial email.
fx of 'orrible cold ib by dose... *SNEEEZE*...
--
http://www.lennard.net.nz/
Ben Lennard, NCEE, Dip EE
Electronics R&D
Hm: +64 4 972 7567
Mb: +64 21 536 627
87 Spencer Street
Crofton Downs
Wellington
New Zealand
"To the optimist, the glass is half full. To the pessimist, the glass is
half empty. To the engineer, the glass is twice as big as it needs to be."
No animals were harmed in the transmission of this email, although the
Dog next door is living on borrowed time, let me tell you! Those of you
with an overwhelming fear of the unknown will be gratified to learn that
there is no hidden message revealed by reading this warning backwards.
> From: "Ray McArthur" <rjmca@u...>
> Reply-To: basicstamps@yahoogroups.com
> Date: Tue, 8 Oct 2002 01:09:13 -0400
> To: <basicstamps@yahoogroups.com>
> Subject: Re: [noparse][[/noparse]basicstamps] OT: Clamping Diodes
>
>
Original Message
> From: "Ben" <ben@l...>
>
>> Not quiet right.
>>
>> The back emf created by a collasping magnetic field of a Relay or solenoid
>> is large (hundreds of volts), as in the example I mentioned before (where
> I
>> measured a -500V spike).
>>
>> So, your clamping diode needs to withstand a few hundred volts, not just
>> have a reverse voltage greater than the voltage of the power supply. So a
>> 1N4007 (1000v reverse voltage, 1A forward current), is the one to go for.
>>
> *************************
> Ben
>
> The hundreds of volts you saw will not happen if the diode clamp is in
> place. The spike happens if there is nowhere for the stored energy to go.
>
> Regards,
> Ray McArthur
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and Body
> of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
discovered that a good portion of the flyback energy is actually shunted
by the capacitive qualities of the diode.
In many designs you will find a small value ceramic cap also in parallel
with the diode, which is in parallel with the relay winding. Layout of
the circuit can also be an influencing factor as the inductive and
capacitive qualities of the interconnecting wiring to the relay can
dampen flyback as well.
There is no such thing as having too fast of a diode to arrest flyback.
Flyback characteristics will also be influenced by the type of material
used as the core in the relay. It is of no consequence whether the
flyback is generated by a high frequency circuit or some slow on/off
action of a relay as the flyback will be governed by the inductive
qualities of the coil (core characteristics included).
When you scope flyback (with a very low ohmic value shunt in series) you
may be surprised to see amperage in the hundreds if not in the thousands
of amps for brief periods (10 to 20 nanoseconds).
If the value of the connected circuitry is high and interconnections to
the relay short, I'd start with an FR803 and a 0.01 ceramic to be on the
safe side.
Timothy Medema wrote:
>
> Good Day Everyone,
>
> This is off topic I know, but maybe others need to know too. I
> need to put a clamping diode across a solenoid coil to protect the drive
> electronics from the turn-off voltage spike. My question is: Can I use a
> general purpose diode here, as long as conditions don't exceed the diodes
> ratings? I'm thinking of the 1N4000 series. Or does this need to be a
> fast recovery diode? Recommendations?
>
> Thanks,
>
> Tim
>
> Timothy Medema
> CrystaLite, Incorporated
> 3307 Cedar St. (425) 745-6000 800-666-6065
> Everett, WA 98201 Fax: (425) 257-0232
>
> www.crystaliteinc.com
> <mailto:timm@c...>timm@c...
>
> The information transmitted is intended only for the person or entity to
> whom it is addressed and may contain confidential and/or privileged
> material. Any review, retransmission, dissemination or other use of, or
> taking of any action in reliance upon, this information by persons or
> entities other than the intended recipient is prohibited. If you received
> this in error, please contact the sender and delete the material from any
> computer.
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and Body
of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
Much appreciated,
Tim
At 07:02 AM 10/9/2002 -0400, you wrote:
>Working with others in the field of high frequency flyback, we've
>discovered that a good portion of the flyback energy is actually shunted
>by the capacitive qualities of the diode.
>
>In many designs you will find a small value ceramic cap also in parallel
>with the diode, which is in parallel with the relay winding. Layout of
>the circuit can also be an influencing factor as the inductive and
>capacitive qualities of the interconnecting wiring to the relay can
>dampen flyback as well.
>
>There is no such thing as having too fast of a diode to arrest flyback.
>Flyback characteristics will also be influenced by the type of material
>used as the core in the relay. It is of no consequence whether the
>flyback is generated by a high frequency circuit or some slow on/off
>action of a relay as the flyback will be governed by the inductive
>qualities of the coil (core characteristics included).
>
>When you scope flyback (with a very low ohmic value shunt in series) you
>may be surprised to see amperage in the hundreds if not in the thousands
>of amps for brief periods (10 to 20 nanoseconds).
>
>If the value of the connected circuitry is high and interconnections to
>the relay short, I'd start with an FR803 and a 0.01 ceramic to be on the
>safe side.
>
>
>
>
>Timothy Medema wrote:
> >
> > Good Day Everyone,
> >
> > This is off topic I know, but maybe others need to know too. I
> > need to put a clamping diode across a solenoid coil to protect the drive
> > electronics from the turn-off voltage spike. My question is: Can I use a
> > general purpose diode here, as long as conditions don't exceed the diodes
> > ratings? I'm thinking of the 1N4000 series. Or does this need to be a
> > fast recovery diode? Recommendations?
> >
> > Thanks,
> >
> > Tim
> >
> > Timothy Medema
> > CrystaLite, Incorporated
> > 3307 Cedar St. (425) 745-6000 800-666-6065
> > Everett, WA 98201 Fax: (425) 257-0232
> >
> > www.crystaliteinc.com
> > <mailto:timm@c...>timm@c...
> >
> > The information transmitted is intended only for the person or entity to
> > whom it is addressed and may contain confidential and/or privileged
> > material. Any review, retransmission, dissemination or other use of, or
> > taking of any action in reliance upon, this information by persons or
> > entities other than the intended recipient is prohibited. If you received
> > this in error, please contact the sender and delete the material from any
> > computer.
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > from the same email address that you subscribed. Text in the Subject
> and Body of the message will be ignored.
> >
> >
> > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
>from the same email address that you subscribed. Text in the Subject and
>Body of the message will be ignored.
>
>
>Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
need to do to protect a triac powering it or is it a non-issue?
the coil.
Tracs and SCRs are very sensitive to spikes. Also remember that these types
of devices are latched on and must be turned off by removing power!
[noparse][[/noparse]Non-text portions of this message have been removed]
across the relay coil! The 1N4000 series diodes can be modeled as an ideal
diode shunted by a capacitor. A fast recovery diode is fabricated to minimize
charge storage (capacitance). Therefore you get the capacitor "for free" with
this type of diode! The core of a relay is iron not a high frequency
ferromagnetic material, the Q of the coil is low, and the driving source is a
slow DC source. Therefore we are not concerned with a resonant ringing
frequency or a repetitive driving source. We turn it on and leave it on then
turn it off and leave it off, etc., etc.
It is good to see people relying on basic principles of electrical circuits
to understand circuit phenomena! Keep up these excellent responses to basic
electronics questions! That is what this site is all about!
[noparse][[/noparse]Non-text portions of this message have been removed]
us! Many thanks to all of you for giving your time and brain power through
helping with this question.
Much appreciated,
Tim
At 12:47 PM 10/9/2002 -0400, you wrote:
>These statements are further reasons to use a "slow" rectifier type of diode
>across the relay coil! The 1N4000 series diodes can be modeled as an ideal
>diode shunted by a capacitor. A fast recovery diode is fabricated to minimize
>charge storage (capacitance). Therefore you get the capacitor "for free" with
>this type of diode! The core of a relay is iron not a high frequency
>ferromagnetic material, the Q of the coil is low, and the driving source is a
>slow DC source. Therefore we are not concerned with a resonant ringing
>frequency or a repetitive driving source. We turn it on and leave it on then
>turn it off and leave it off, etc., etc.
>It is good to see people relying on basic principles of electrical circuits
>to understand circuit phenomena! Keep up these excellent responses to basic
>electronics questions! That is what this site is all about!
>
>
>[noparse][[/noparse]Non-text portions of this message have been removed]
>
>
>To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
>from the same email address that you subscribed. Text in the Subject and
>Body of the message will be ignored.
>
>
>Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>Relays that use AC just have a built in diode to change the AC to DC to
>run the coil.
Although some relays may be made that way, that doesn't match with my
general experience at all. Relays actuated by an AC solenoid coil
generally have laminated solenoid cores to prevent the chattering or
vibration that might otherwise result.
>Tracs and SCRs are very sensitive to spikes. Also remember that these types
>of devices are latched on and must be turned off by removing power!
In the absence of a driving signal, both of these devices turn off when
current ceases to flow. For a triac switching AC this occurs 120 times a
second. Turning off these devices when they are used to switch relatively
pure DC (no true zero voltage) requires interrupting the power, or else a
turn-off circuit that is capable of momentarily providing an appropriate
reverse bias. The latter isn't exactly a trivial matter unless some
integrated solution I don't know about is available - which is entirely
possible.
73 de Jim, KB3PU
>What about relays that use AC coil current? Is there anything you
>need to do to protect a triac powering it or is it a non-issue?
I use a series RC snubber with most of my triac circuits. For 120 Vac,
appropriate values are 100n 400V film capacitor in series with 10R
1/4W. The snubber is connected across the triac terminals MT1 & MT2.
If I am using a relay to control a large AC contactor or solenoid, I
usually connect a small 130V MOV across the contactor's coil terminals.
dwayne
--
Dwayne Reid <dwayner@p...>
Trinity Electronics Systems Ltd Edmonton, AB, CANADA
(780) 489-3199 voice (780) 487-6397 fax
Celebrating 18 years of Engineering Innovation (1984 - 2002)
.-. .-. .-. .-. .-. .-. .-. .-. .-. .-
`-' `-' `-' `-' `-' `-' `-' `-' `-'
Do NOT send unsolicited commercial email to this email address.
This message neither grants consent to receive unsolicited
commercial email nor is intended to solicit commercial email.
flow...that is what I meant when I stated that power must be removed to turn
it off. Although this actually occurs 60 times per second if using straight
AC 60 Hz power rather than 120 times a second as you stated.
As for AC relays using special laminates...I am not familiar with them but I
don't understand how they would keep the magnetic field constant enough to
hold the armature closed during the entire + to - cycling of the AC waveform!
Please enlighten me! (learn something new every day!)
[noparse][[/noparse]Non-text portions of this message have been removed]
out the relays my buddy has already have protection built in so I
don't have to worry about it but, it'd be a good addition to my book
of datasheets and formulas [noparse]:D[/noparse]
>You are indded correct that a Triac or SCR turns off when curent ceases to
>flow...that is what I meant when I stated that power must be removed to turn
>it off. Although this actually occurs 60 times per second if using straight
>AC 60 Hz power rather than 120 times a second as you stated.
I'm sorry, but a full AC cycle contains TWO zero crossings. If you
consider one cycle starts at zero, there's one crossing, then it rises to a
peak and drops to a negative peak (crossing thru the second zero) and then
back up to zero where the next cycle starts. We'll count that last
crossing as the first crossing of the next cycle. By that rather simple
analysis that's 60 Hz or 120 zero crossings per second. In Europe, make
that 50 Hz and 100 zero crossings.
>As for AC relays using special laminates...I am not familiar with them but I
>don't understand how they would keep the magnetic field constant enough to
>hold the armature closed during the entire + to - cycling of the AC waveform!
>Please enlighten me! (learn something new every day!)
I'm afraid I'd have a hard time explaining the physics of this, but I know
it works. I think it has to do with lower core loses in laminated cores
allowing the field in the core to persist long enough to avoid
chatter. But don't take that to the bank. Give it a few hours, or until
tomorrow morning and someone who REALLY knows will probably explain to both
of us.
One thing I can tell you for sure about magnetics (and this is sort of
tongue in cheek) is that a lot of things that seem logical prior to deeper
exposure to this sort of thing will lead you to assumptions that will bear
no resemblance to the way things really work.
Jim H
> it works. I think it has to do with lower core loses in laminated
cores
> allowing the field in the core to persist long enough to avoid
> chatter. But don't take that to the bank. Give it a few hours,
or until
> tomorrow morning and someone who REALLY knows will probably
explain to both
> of us.
I think you have it right. Back in fleet school I was taught this -
14 years ago... I don't remember the details but I do vaguely
remember seeing layers of metal and those layers being what
prevented chatter. That was the last time I even thought about the
topic until now though...
Lets hope one of the hacksperts clears this up. Now that I've been
bitten by the stamp I want to re-learn everything I've forgotten
over 14 years.
When I first started hacking my way through electronics, about 25 years
ago, which included reading everything I could fasten my hands on to.
And asking a Wookiee's howl sized amount of questions, as well. This is
what I found out about transformers: That's why the people who invented
the current design theory behind transformers decided. Fleet school?
Whose? Ours? Canada's? Which? By the way that wasn't free advice. One of
you owes me money. Or something.
Gregg C Levine hansolofalcon@w...
"The Force will be with you...Always." Obi-Wan Kenobi
"Use the Force, Luke."· Obi-Wan Kenobi
(This company dedicates this E-Mail to General Obi-Wan Kenobi )
(This company dedicates this E-Mail to Master Yoda )
>
Original Message
> From: ghidera2000 [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=niHtHkPq-_hzZx_jHOCmyE-WH1DO4RjMp6lbkO8_RQ_1cCpFfGJCpIBg8dn1jrCbZyjldWQ5jHOrXoOwRkU]ghidera2000@y...[/url
> Sent: Wednesday, October 09, 2002 9:35 PM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] Re: OT: Clamping Diodes
>
> --- In basicstamps@y..., Jim Higgins <HigginsJ@s...> wrote:
> > it works. I think it has to do with lower core loses in laminated
> cores
> > allowing the field in the core to persist long enough to avoid
> > chatter. But don't take that to the bank. Give it a few hours,
> or until
> > tomorrow morning and someone who REALLY knows will probably
> explain to both
> > of us.
>
> I think you have it right. Back in fleet school I was taught this -
> 14 years ago... I don't remember the details but I do vaguely
> remember seeing layers of metal and those layers being what
> prevented chatter. That was the last time I even thought about the
> topic until now though...
>
> Lets hope one of the hacksperts clears this up. Now that I've been
> bitten by the stamp I want to re-learn everything I've forgotten
> over 14 years.
120 times per second the device will switch off...but since an SCR only
conducts in one direction, it will only "see" 60 of these zero crossings!
Thanks for reminding me that a TRIAC actually does "see" all 120 of these
zero crossings!
[noparse][[/noparse]Non-text portions of this message have been removed]
>Now that I've been bitten by the stamp I want to re-learn everything I've
>forgotten over 14 years.
Yeah, it's probably a case of use it or lose it and have to relearn it - or
at least be reminded. But be careful. There might be one or two things
you're better off leaving forgotten. ;-)
73 de Jim, KB3PU
>You are indeed correct about the 120 zero crossings... so for a Triac indeed
>120 times per second the device will switch off...but since an SCR only
>conducts in one direction, it will only "see" 60 of these zero crossings!
>Thanks for reminding me that a TRIAC actually does "see" all 120 of these
>zero crossings!
Well... zero is zero is zero, or so I'd assume, but then I'm the guy who
recently suggested assuming was risky. Anyhow, since I'm not 100% sure
whether an SCR will switch off at each of 120 zero crossings per second (60
Hz AC) or only on 60 of them, I'll sit by and hope for a second opinion.
Jim H
>Well... zero is zero is zero, or so I'd assume, but then I'm the guy who
>recently suggested assuming was risky. Anyhow, since I'm not 100% sure
>whether an SCR will switch off at each of 120 zero crossings per second (60
>Hz AC) or only on 60 of them, I'll sit by and hope for a second opinion.
Well . . . here goes.
Assuming this is straight AC, the SCR will conduct on alternate half
cycles. The SCR does not conduct when reverse biased. So I'd say 60.
dwayne
--
Dwayne Reid <dwayner@p...>
Trinity Electronics Systems Ltd Edmonton, AB, CANADA
(780) 489-3199 voice (780) 487-6397 fax
Celebrating 18 years of Engineering Innovation (1984 - 2002)
.-. .-. .-. .-. .-. .-. .-. .-. .-. .-
`-' `-' `-' `-' `-' `-' `-' `-' `-'
Do NOT send unsolicited commercial email to this email address.
This message neither grants consent to receive unsolicited
commercial email nor is intended to solicit commercial email.
>At 07:03 PM 10/10/02 -0400, Jim Higgins wrote:
>
> >Well... zero is zero is zero, or so I'd assume, but then I'm the guy who
> >recently suggested assuming was risky. Anyhow, since I'm not 100% sure
> >whether an SCR will switch off at each of 120 zero crossings per second (60
> >Hz AC) or only on 60 of them, I'll sit by and hope for a second opinion.
>
>Well . . . here goes.
>
>Assuming this is straight AC, the SCR will conduct on alternate half
>cycles. The SCR does not conduct when reverse biased. So I'd say 60.
Well... OK... but only because you've got the AC waveform in your sig
(below) to back it up. ;-)
Jim H
>Dwayne Reid <dwayner@p...>
>Trinity Electronics Systems Ltd Edmonton, AB, CANADA
>(780) 489-3199 voice (780) 487-6397 fax
>
>Celebrating 18 years of Engineering Innovation (1984 - 2002)
> .-. .-. .-. .-. .-. .-. .-. .-. .-. .-
> `-' `-' `-' `-' `-' `-' `-' `-' `-'
>Do NOT send unsolicited commercial email to this email address.
>This message neither grants consent to receive unsolicited
>commercial email nor is intended to solicit commercial email.