RE: [AMRadio] Relay 101
Although simplistic, those papers are well written. My only caveat is that they are written for electromechanical relays. Reed relays (my area) have some characteristics taht are very similar and some that are quite different. Nice find Jim. 73, Mark W1EOF -Original Message- From: Jim Candela [mailto:[EMAIL PROTECTED] Sent: Wednesday, March 22, 2006 12:13 PM To: Discussion of AM Radio Subject: [AMRadio] Relay 101 Hi All, The Tyco folks have some interesting application notes about relays that fit into an earlier thread on this reflector. Check out the following links: Relay Coil Back EMF protection: http://relays.tycoelectronics.com/app_pdfs/13c3311.pdf Relay Contact Arc suppression: http://relays.tycoelectronics.com/app_pdfs/13c3236.pdf Other Relay and general switching topics: http://relays.tycoelectronics.com/application.asp We can use some of these ideas on our AM rigs Jim WD5JKO __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.385 / Virus Database: 268.2.6/287 - Release Date: 3/21/06 -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.385 / Virus Database: 268.2.6/287 - Release Date: 3/21/06
RE: [AMRadio] Relay 101 Reed Relays
Mark, Would you elaborate on some of the subtleties of the reed relay characteristics? They are so prevalent now in many tuners and even my Philips RF gen that it would be interesting to learn something about them besides the basic functionality. TNX de KA4JVY Mark --- W1EOF [EMAIL PROTECTED] wrote: Although simplistic, those papers are well written. My only caveat is that they are written for electromechanical relays. Reed relays (my area) have some characteristics taht are very similar and some that are quite different. Nice find Jim. 73, Mark W1EOF -Original Message- From: Jim Candela [mailto:[EMAIL PROTECTED] Sent: Wednesday, March 22, 2006 12:13 PM To: Discussion of AM Radio Subject: [AMRadio] Relay 101 Hi All, The Tyco folks have some interesting application notes about relays that fit into an earlier thread on this reflector. Check out the following links: Relay Coil Back EMF protection: http://relays.tycoelectronics.com/app_pdfs/13c3311.pdf Relay Contact Arc suppression: http://relays.tycoelectronics.com/app_pdfs/13c3236.pdf Other Relay and general switching topics: http://relays.tycoelectronics.com/application.asp We can use some of these ideas on our AM rigs Jim WD5JKO __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.385 / Virus Database: 268.2.6/287 - Release Date: 3/21/06 -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.385 / Virus Database: 268.2.6/287 - Release Date: 3/21/06 __ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
RE: [AMRadio] Relay 101 Reed Relays
Well like machanical relays it's very much about the contact materials. In the relay business we spend a lot of time working on contact materials, plating, etc. So it's hard to illuminate too much without knowing the particular device in question. What's a reed-relay? A relay made from a reed-switch inside a coil. A reed switch has two ferrous blades which have had a contact material deposited on the ends making up the contact. When the coil is energized the steel blades of the reed switch deflect a very small amount and close the contacts. That's it. A few thoughts: 1. Reed relays tend to be fast. Regular reeds close in less than a millisecond, mercury reeds about 2ms. 2. If you don't know what the coil spec is, hookup the coil across a variable power supply. Adjust the meter upward slowly until the contacts close (determined by a DMM across them). Bring the coil voltage to 0.00 and repeat a few times. This is call the Operate voltage. Normal operate voltage for a reed relay is 50% overdive. So your typical 5.0vdc relay will operate about 3.6 volts or so. Most relays are find at 100% overdrive, it doesn't hurt the relay. 3. Contact life is all about the materials. When designing a generic multi-purpose reed relay they choose a reed switch which can handle moderate voltages and loads. In very broad general terms if you were interested in very very low contact resistance you use a soft contact surface like gold. This is terrible for higher voltages or currents though. For those you want something really hard. 4. If you have a mercury or a mercury-wetted relay make sure it's oriented properly. These relays have a blob (or at least some small balls) of mercury in them. You don't want that mercury floating around and shorting the contacts when the relay is supposed to be off. They will sometimes have an arrow on them but not always. 5. Form-B reed relays rely on a magnet to hold the switch closed. When you apply voltage to the coil the magnetic force overcomes the magnet and opens the switch. 6. Form-C reed relays are made with a form-c switch. The blade is held against the N.C. contact via mechanical force. Applying coil voltage results in magnetic force that moves the blade from the N.C. contact to the N.O. contact. It relys on mechanical force to return the switch to the resting state. 7. Reed relays can have two types of shields in them. One is a magnetic shield on the outside of the coil. This helps prevent interaction when the relays are mounted very close to one another on a PC board. The other is a RF shield inside the bore of the coil. This is to provide a constant impedance to the circuit. This is very, very important to many reed relay customers. For instance automatic test equipment (ATE) manufacturers are big consumers of reed relays. A modern semiconductor tester can use 10,000 relays. They want to test fast device quickly. So they are very very concerned with the RF performance of the device. Many years ago I started working for a reed relay company. I was naive, thinking How complicated can these things be?' Ha! Now I'm older and wiser and understand that there is a wealth of knowledge and complexity in many things we deam simple. Reed relays incorporate electronics, physics, magnetics into their design and use. TO design and test them you work with voltages from microvolts to thousands of volts. .001 ohm to 10^12 ohms (million-megohms). I'm still learning today after twenty years. Relay manufacturers are constantly pushing the envelope to make devices which not only perform better but are much smaller and less expensive. I have recently seen reed relays that are approximately the same size as a 1/2W resistor! I don't know what else to say in general about them. I'll be glad to answer any questions on this subject. I hope this gives you some food for thought. 73, Mark W1EOF -Original Message- From: Mark Foltarz [mailto:[EMAIL PROTECTED] Sent: Thursday, March 23, 2006 12:24 PM To: amradio@mailman.qth.net Subject: RE: [AMRadio] Relay 101 Reed Relays Mark, Would you elaborate on some of the subtleties of the reed relay characteristics? They are so prevalent now in many tuners and even my Philips RF gen that it would be interesting to learn something about them besides the basic functionality. TNX de KA4JVY Mark --- W1EOF [EMAIL PROTECTED] wrote: Although simplistic, those papers are well written. My only caveat is that they are written for electromechanical relays. Reed relays (my area) have some characteristics taht are very similar and some that are quite different. Nice find Jim. 73, Mark W1EOF -Original Message- From: Jim Candela [mailto:[EMAIL PROTECTED] Sent: Wednesday, March 22, 2006 12:13 PM To: Discussion of AM Radio Subject: [AMRadio] Relay 101 Hi All, The Tyco folks have some interesting application notes about relays that fit into an earlier thread on this reflector.
Re: [AMRadio] Relay 101 Reed Relays
Mark, I don't know about everyone else, but I truly appreciate the information. I've used reed relays in the past, but certainly didn't and don't know much about them. Your info helped clear up some questions. Thanks, Rick/K5IZ W1EOF wrote: Well like machanical relays it's very much about the contact materials. In the relay business we spend a lot of time working on contact materials, plating, etc. So it's hard to illuminate too much without knowing the particular device in question. What's a reed-relay? A relay made from a reed-switch inside a coil. A reed switch has two ferrous blades which have had a contact material deposited on the ends making up the contact. When the coil is energized the steel blades of the reed switch deflect a very small amount and close the contacts. That's it. A few thoughts: 1. Reed relays tend to be fast. Regular reeds close in less than a millisecond, mercury reeds about 2ms. 2. If you don't know what the coil spec is, hookup the coil across a variable power supply. Adjust the meter upward slowly until the contacts close (determined by a DMM across them). Bring the coil voltage to 0.00 and repeat a few times. This is call the Operate voltage. Normal operate voltage for a reed relay is 50% overdive. So your typical 5.0vdc relay will operate about 3.6 volts or so. Most relays are find at 100% overdrive, it doesn't hurt the relay. 3. Contact life is all about the materials. When designing a generic multi-purpose reed relay they choose a reed switch which can handle moderate voltages and loads. In very broad general terms if you were interested in very very low contact resistance you use a soft contact surface like gold. This is terrible for higher voltages or currents though. For those you want something really hard. 4. If you have a mercury or a mercury-wetted relay make sure it's oriented properly. These relays have a blob (or at least some small balls) of mercury in them. You don't want that mercury floating around and shorting the contacts when the relay is supposed to be off. They will sometimes have an arrow on them but not always. 5. Form-B reed relays rely on a magnet to hold the switch closed. When you apply voltage to the coil the magnetic force overcomes the magnet and opens the switch. 6. Form-C reed relays are made with a form-c switch. The blade is held against the N.C. contact via mechanical force. Applying coil voltage results in magnetic force that moves the blade from the N.C. contact to the N.O. contact. It relys on mechanical force to return the switch to the resting state. 7. Reed relays can have two types of shields in them. One is a magnetic shield on the outside of the coil. This helps prevent interaction when the relays are mounted very close to one another on a PC board. The other is a RF shield inside the bore of the coil. This is to provide a constant impedance to the circuit. This is very, very important to many reed relay customers. For instance automatic test equipment (ATE) manufacturers are big consumers of reed relays. A modern semiconductor tester can use 10,000 relays. They want to test fast device quickly. So they are very very concerned with the RF performance of the device. Many years ago I started working for a reed relay company. I was naive, thinking How complicated can these things be?' Ha! Now I'm older and wiser and understand that there is a wealth of knowledge and complexity in many things we deam simple. Reed relays incorporate electronics, physics, magnetics into their design and use. TO design and test them you work with voltages from microvolts to thousands of volts. .001 ohm to 10^12 ohms (million-megohms). I'm still learning today after twenty years. Relay manufacturers are constantly pushing the envelope to make devices which not only perform better but are much smaller and less expensive. I have recently seen reed relays that are approximately the same size as a 1/2W resistor! I don't know what else to say in general about them. I'll be glad to answer any questions on this subject. I hope this gives you some food for thought. 73, Mark W1EOF
RE: [AMRadio] Relay 101 Reed Relays (white papers)
Below are links to some white papers that explain reed relays much better than I can. Enjoy. 73, Mark W1EOF ~~~ How a reed switch operates: http://www.cotorelay.com/Reed_Switch_Operation_Methods.pdf Glossary of reed switch terms: http://www.cotorelay.com/Glossary.pdf Switching considerations of contacts: http://www.cotorelay.com/Switching_Considerations.pdf RF Characteristics of reed relays: http://www.cotorelay.com/RF_Parameter_Measurement.pdf Contact Resistance and Dynamics: http://www.cotorelay.com/Contact_Resistance___Dynamics.pdf Magnetic Interaction: http://www.cotorelay.com/Magnetic_Interaction.pdf -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.385 / Virus Database: 268.3.0/290 - Release Date: 3/23/06
