I think Cliff's got a pretty good pragmatic answer. I have learned not to discount any claims about voodoo because I learned that some of them are true...then there are others I have to draw the line at for reasons of practicality and sanity.
Alot of times when a particular component technology is disparaged for reliability reasons, it is sometimes because it was misused. I worked somewhere people decided certain brands of op amps were bad because their active filters oscillated - HELLO, do you SMELL how crappy your design is? It doesn't work with the op amps that are closer to ideal (higher gain) -sorry ,off topic...
I personally have never used mercury wetted relays for audio - so I don't know. I liked them in the days of tubes (oh, wait, we ARE still in the days of tubes) because the contacts are more forgiving about not welding when switching bigger things that audio.
Alot of times when a particular component technology is disparaged for reliability reasons, it is sometimes because it was misused. I worked somewhere people decided certain brands of op amps were bad because their active filters oscillated - HELLO, do you SMELL how crappy your design is? It doesn't work with the op amps that are closer to ideal (higher gain) -sorry ,off topic...
I personally have never used mercury wetted relays for audio - so I don't know. I liked them in the days of tubes (oh, wait, we ARE still in the days of tubes) because the contacts are more forgiving about not welding when switching bigger things that audio.
fotios said:
jacco vermeulen said:
jacco vermeulen said:
Bravo Jacco. Exactly this information i wanted. Thanks man, you make my day because already i have bought 12 pieces of DS2E of NAIS from my local supplier before one week (fortunatelly NAIS is distributed in Greece and the local distributor has stock!). I am obliged to you. Now i can go to sleep. Tell me your address to send you a bottle of "CHIPOURO' of much more higher quality from "OUZO".
Fotios
Re: Use sealed reed relays
Thanks Cliff for your really esential information. This type of reed relays you refer has contacts from Gold coated or mixed with Ruthenium (a member of platine familly) and marked as "Ru" usually. Thanks again for your precious experience offered.
Fotios
cliff said:
Thanks Cliff for your really esential information. This type of reed relays you refer has contacts from Gold coated or mixed with Ruthenium (a member of platine familly) and marked as "Ru" usually. Thanks again for your precious experience offered.
Fotios
Hi Fotios,
Many telecom relays are also gas sealed types. Inert of course.
Hi Sandy,
Isolating the ground from all video sources would be very worthwhile. Things like tuners (unless connected to cable antenna) and CD players would not have very much noise on their grounds.
Excellent point though. Using a dual deck, four contact rotary switch might be the best plan. Ground sections make before break to avoid a "no ground" hum that may occur.
-Chris
Many telecom relays are also gas sealed types. Inert of course.
There are two things you can do here. Shape the on and off current ramps. Run the coil from a clean supply. Then there will be no noise emitted from the coil.
Hi Sandy,
Isolating the ground from all video sources would be very worthwhile. Things like tuners (unless connected to cable antenna) and CD players would not have very much noise on their grounds.
Excellent point though. Using a dual deck, four contact rotary switch might be the best plan. Ground sections make before break to avoid a "no ground" hum that may occur.
-Chris
Rotary switch or relays
Chris
Inevitably , when you have a full complement of inputs from various sources, and piles of cables, audio,video and SPDIF, together behind a cabinet, and you turn up to full gain, when the grounds are also switched you will hear different levels of hum from many sources, From some sources there will be dead silence. This method allows you to isolate the poorer inputs, and optimise cable routing etc. Perhaps even to improve the equipment that does not respond to better cable routing clear of mains leads.
Regards
Alex
Chris
Inevitably , when you have a full complement of inputs from various sources, and piles of cables, audio,video and SPDIF, together behind a cabinet, and you turn up to full gain, when the grounds are also switched you will hear different levels of hum from many sources, From some sources there will be dead silence. This method allows you to isolate the poorer inputs, and optimise cable routing etc. Perhaps even to improve the equipment that does not respond to better cable routing clear of mains leads.
Regards
Alex
If you're worried about electromagnetic interference from the energised coil, you can use latching relays, which don't use any power once switched. This could alleviate your concerns.
I have been using relays mounted at the RCA input point for abour 12 years and I find them far superior to switches. Prior to that I used switches but these became very noisy after only a few years and were a pain to clean. Go relays for a hassle free long life (use the best quality)
I have been using relays mounted at the RCA input point for abour 12 years and I find them far superior to switches. Prior to that I used switches but these became very noisy after only a few years and were a pain to clean. Go relays for a hassle free long life (use the best quality)
TO ALL
Many thanks to all of you which show so much interest for my speculation. Up to now almost all of you (included myself) prefer the use of an open type rotary switch with a long distance between the two decks of two channels as we have a good crosstalk. This is very right sure, and without doubt the use of such switch appears as the better solution. It should I mark here that the long life of contacts and the need of cleaning of these does not interest me so much. It is a usual maintenance work and all of us (as I suppose from that you write all of you today-what a nice meeting of craftsmen!!!) we are familiarized with such type work. It should not we forget that the bigger part of our life expensed in maintenance and repair works and the smallest in theoretical objects. The problem with rotary style switches it is that; the high quality are very expensive. I have found in the sites of two companies two types of incredible quality and flexibility (in the style of kit where you can make any combination and number of poles) but the parts are very expensive and are sold separately. I calculated what needs such switch to it is made, and I was dazed when I saw that the cost of kit reached in the 100€ roughly! Let we see now the case of relays. I feel really idiot from the phobia that I expressed in my initial post, that I am afraid the electromagnetic interference which caused when the coil is activated. I supposed that a relay to keep closed his contacts it must flow current continuously in his coil. Thanks to the information of friend Jacco Vermeulen I discovered that this is not essential because the existence of Latching Relays. Their operation is precisely same with this of a push button latching switch such as the power switch of audio devices or televisions and become via mechanic parts. We can name him also bistable. In the industry they are reported as power saving relays. And this is owed in that to changes place the contact is enough the momentary action of coil. That is to say via an auxiliary mechanism the contacts lock between them and remain so until the activation of the coil again. Thus is resolved the problem of electromagnetic interference as the coil does not need continuous power to retains his contacts in a place. There are two types of latching relays; with single coil and with double coil. In the case of single coil to becomes change of the place of contact is inverted the polarity of coil supply. In the case of double coil, each one of the coils when powered operate respectively as set and reset; thus does not exist need of inversion of polarity. Simply is activated the one of the two coils each time. From as long as I searched exists a big variety from such type of relays (SPCO or DPCO) and except Panasonic or NAIS they are also offered from other known companies such as Finder, Omron, etc in very good prices. Panasonic are some expensive about 12€. Omron and Finder also NAIS (Matsushita) offers more economic about 7 to 8€. All have exceptional quality contacts, starting from gold and reaching up to alloy of gold and Palladium or Ruthenium and are mainly of sealed type. Depending on the alloy of contact is increased also the price. Their unique disadvantage is the unpredictable place of their contacts during supplying the appliance in which contained. It is of volatile type. This is indeed a big problem as you can imagine during supplying the preamplifier the CD the tuner and the phono can be found connected simultaneously in the input buffer. I believe however that this problem can resolved easily with the use of a timer as 555 in such way like the delay protection in amplifiers. I will search this and I will report the way that can become precisely. Perhaps and with the use of a cheap BCD rotary switch.
Fotios
Many thanks to all of you which show so much interest for my speculation. Up to now almost all of you (included myself) prefer the use of an open type rotary switch with a long distance between the two decks of two channels as we have a good crosstalk. This is very right sure, and without doubt the use of such switch appears as the better solution. It should I mark here that the long life of contacts and the need of cleaning of these does not interest me so much. It is a usual maintenance work and all of us (as I suppose from that you write all of you today-what a nice meeting of craftsmen!!!) we are familiarized with such type work. It should not we forget that the bigger part of our life expensed in maintenance and repair works and the smallest in theoretical objects. The problem with rotary style switches it is that; the high quality are very expensive. I have found in the sites of two companies two types of incredible quality and flexibility (in the style of kit where you can make any combination and number of poles) but the parts are very expensive and are sold separately. I calculated what needs such switch to it is made, and I was dazed when I saw that the cost of kit reached in the 100€ roughly! Let we see now the case of relays. I feel really idiot from the phobia that I expressed in my initial post, that I am afraid the electromagnetic interference which caused when the coil is activated. I supposed that a relay to keep closed his contacts it must flow current continuously in his coil. Thanks to the information of friend Jacco Vermeulen I discovered that this is not essential because the existence of Latching Relays. Their operation is precisely same with this of a push button latching switch such as the power switch of audio devices or televisions and become via mechanic parts. We can name him also bistable. In the industry they are reported as power saving relays. And this is owed in that to changes place the contact is enough the momentary action of coil. That is to say via an auxiliary mechanism the contacts lock between them and remain so until the activation of the coil again. Thus is resolved the problem of electromagnetic interference as the coil does not need continuous power to retains his contacts in a place. There are two types of latching relays; with single coil and with double coil. In the case of single coil to becomes change of the place of contact is inverted the polarity of coil supply. In the case of double coil, each one of the coils when powered operate respectively as set and reset; thus does not exist need of inversion of polarity. Simply is activated the one of the two coils each time. From as long as I searched exists a big variety from such type of relays (SPCO or DPCO) and except Panasonic or NAIS they are also offered from other known companies such as Finder, Omron, etc in very good prices. Panasonic are some expensive about 12€. Omron and Finder also NAIS (Matsushita) offers more economic about 7 to 8€. All have exceptional quality contacts, starting from gold and reaching up to alloy of gold and Palladium or Ruthenium and are mainly of sealed type. Depending on the alloy of contact is increased also the price. Their unique disadvantage is the unpredictable place of their contacts during supplying the appliance in which contained. It is of volatile type. This is indeed a big problem as you can imagine during supplying the preamplifier the CD the tuner and the phono can be found connected simultaneously in the input buffer. I believe however that this problem can resolved easily with the use of a timer as 555 in such way like the delay protection in amplifiers. I will search this and I will report the way that can become precisely. Perhaps and with the use of a cheap BCD rotary switch.
Fotios
smithy666 said:
Smithy666
I hope in your comprehension because actually we say the same thing. You anticipated me, because i need more time from you to translate my thought from Greek to English. It is a disadvantage to me. The same happened in the morning (time in Greece) today and i had recalled a big reply which was maden with big labour as you understand. Thanks for your reply.
Fotios
smithy666 said:
Hi smithy666
Today i have spent my time to study the latching relays. Indeed they are a very good solution and don't have any problem with the position of their contacts when the device is supplied because the latching achived with mechanical parts or a passive magnet. So the latching does not has relation with any electric method thus the latching relays can called as non-volatile. BTW i discovered that except the expensive Panasonic offered also from OMRON in competitive quality and almost in half price (about 6,5 to 7 euros). A little problem it is the control method because a latching relay to change state it need only a momentary pulse and this is exactly his benefit. Up to now i have thinked 2 or 3 control methods but i have long way yet to finished. One type it is with the use of a binarry up-down counter and a multiplexer, another it is with the use of the 555 well known counter and this seems to be like the better because the 555 has the possibility to produce a momentary pulse and returns in its low state in the monostable mode. The bcd counter has the beneffit of using two beutyfull momentary buttons (up-down) in the front panell to select the input but this implementation it is more difficult. If i will try hard for 2 or 3 days sure i will find the solution. Byt and only the think of this it is frighten me.
I have expensed many time of my life in digital circuits also. Thus, any help or any ready solution it is well appreciated. Thanks for your help from previous.
Fotios
I have an idea for the control. A rotary switch 4 pole, 10 pos (max) coupled to BCD to decimal encoder. The output of the decoder goes to ten "H" bridge motor driver's providing the DIRECTION input. All of the NOT enables then are OR'ed together to a de-bounced push button. This would control 10 single coil latching relays.
Operation then becomes, select a source, then push a button. This has the advantage that you don't have to "click" through every other source to select the one you want. The inversion comes naturally. The H bridge's direction input effectively selects the polarity using a single supply.
A power-up would automatically push the select button.
What whould be cool, is when the rotary switch was moved, and indicator would go from green to yellow until the pointed to source was actually selected (button pushed).
A brief, timed mute could occur here are well.
This might me accomplished by latching the value of the switch with a D flip flop on power-up and when the button is pressed and do a compare with the present value of the switch.
"H" bridges come in all sorts of flavors and power levels. I used them to control a model crane gantry nearly 20 years ago.
PS:
There is actually two other types of latching relays. One is something like a bi-stable impulse relay and another which I haven't seen in a long time where each pulse would advance the contact by one like in the old telephone exchanges. The two types single and dual coil are the most common now.
Hey, I'm just rambling. Just thoughts.
Operation then becomes, select a source, then push a button. This has the advantage that you don't have to "click" through every other source to select the one you want. The inversion comes naturally. The H bridge's direction input effectively selects the polarity using a single supply.
A power-up would automatically push the select button.
What whould be cool, is when the rotary switch was moved, and indicator would go from green to yellow until the pointed to source was actually selected (button pushed).
A brief, timed mute could occur here are well.
This might me accomplished by latching the value of the switch with a D flip flop on power-up and when the button is pressed and do a compare with the present value of the switch.
"H" bridges come in all sorts of flavors and power levels. I used them to control a model crane gantry nearly 20 years ago.
PS:
There is actually two other types of latching relays. One is something like a bi-stable impulse relay and another which I haven't seen in a long time where each pulse would advance the contact by one like in the old telephone exchanges. The two types single and dual coil are the most common now.
Hey, I'm just rambling. Just thoughts.
Digital Control For Input Selection
After two days of exhaustive thought, finally I led to the following drawing for the control of Latching Relays. As we said already these have appreciable advantages in relation with rotary switches and provided that they need a momentary pulse to change place their contacts (does not need continuous application of power in the inductor for the holding of contacts) consequently they do not offer electromagnetic interference in the low level input signal. Also, from my research it resulted that the type with independent coils for set and reset it is preferable, because is simpler his control. Moreover it does not have difference in the price from the type of single coil. If we examine the system from the cost view, a set for 8 inputs it costs with the control circuit from 50 to 60 €. A rotary switch of this quality, it costs from 30 to 40€. I tried to draw a circuit as long as he becomes more functional, and thus I resulted to use of momentary action push button as it is more easily in mounting and more elegant in the face of preamplifier. Also, in order to be accessible in the construction from each one, I excluded the use of microcontroller. Moreover the circuit is not big and includes only11 IC that are very common and can find easily them each one. It may pointed out that the circuit is in form of block diagram as they do not appear the transistors that are between coils and 4066 as output buffers. Each one it has certain knowledge from logic ICs it is very easy to implement this circuit. For each one he does not have such knowledge, it will be waits for few days until I implement the circuit, and I give the normal drawing. Also because logic circuits it is complicated and unforeseen sometimes, maybe the drawing needs certain small changes. In general from my experience I believe that it will function correctly.
The logic of circuit is separated in three parts. Á) Each time is pressed the up or down button only one relay set and all the others simultaneously reset. B) During the activation of preamplifier a master reset executed to avoid any false of activating two or more relays simultaneously, thus each time the first relay will be activated always. The system it is something between volatile and non-volatile type. C) The circuit is easily expandable to drive any type of indicator of the input selected as I thing so. Let us to see a brief explanation of the logic used. During the supply of preamplifier the 556C reset the up-down counter M74HC192 which may be noted that is the only available in the market with separate count-up and count-down inputs from ST because the only equivalent SN74LS192 of Motorola it is obsolete. It is a decade counter. The 556F serves to keep all the analog switches 4066 activated during reset as the signal can be passing to coils. This procedure it lasts for 5 seconds for certainty. During input selection procedure when the button up or down is pressed, then by triggering the corresponding 556A or 556B monostables which drives his output in high state for 0,5sec this translated from inverter HC04 in low state in the input of counter. For the time of 0,5sec the counter does not change state but after the output of 556A is released and goes in his low state again, this translated from HC04 in a positive going pulse in the input of counter so it counts by one changing the state of his outputs. If the button it is pressed continuously then the 556A or 556B start to operate as a pulse generator causing thus the continuous up or down counting of HC192. Because we have to control 8 relays, when the counter reaches the BCD 8 his output Q3 goes high and then resets the counter which starts again to count from 0. The output code of Q0, Q1, Q2, it drives simultaneously the address inputs of the two decoders HC259 and HC138. The HC138 it is a clear 1 of 8 decoder/demultiplexer while HC259 it is a mixed type IC which can be operate as addressable latch or as memory and as 8 line demultiplexer exactly as HC138. The difference between theme it is that HC138 has negative output logic instead HC259 has positive output logic. We need the two opposite logics for the proper operation of set and reset the relays. It is not possible to I include the truth table because his size. Generally when, let to say, X0 output it is high, X1-X7 outputs are low and in the contrary in HC138 the Y0 out is low and Y1-Y7 outputs are high; and so on. For the momentary transfer (NOT continuous!) of the output state of HC259 and HC138 in the coils mediates the 4 analog switches 4066. These activated in synchronous mode with each count up or count down via the monostable 556D and 556E. The only difference it is that the 556D and 556E when triggered remain in high output state (activating thus the 4066) for 1sec, the double time from the 556A – 556B, thus ensures that the data will be passed with assurance in the coils.
Fotios
After two days of exhaustive thought, finally I led to the following drawing for the control of Latching Relays. As we said already these have appreciable advantages in relation with rotary switches and provided that they need a momentary pulse to change place their contacts (does not need continuous application of power in the inductor for the holding of contacts) consequently they do not offer electromagnetic interference in the low level input signal. Also, from my research it resulted that the type with independent coils for set and reset it is preferable, because is simpler his control. Moreover it does not have difference in the price from the type of single coil. If we examine the system from the cost view, a set for 8 inputs it costs with the control circuit from 50 to 60 €. A rotary switch of this quality, it costs from 30 to 40€. I tried to draw a circuit as long as he becomes more functional, and thus I resulted to use of momentary action push button as it is more easily in mounting and more elegant in the face of preamplifier. Also, in order to be accessible in the construction from each one, I excluded the use of microcontroller. Moreover the circuit is not big and includes only11 IC that are very common and can find easily them each one. It may pointed out that the circuit is in form of block diagram as they do not appear the transistors that are between coils and 4066 as output buffers. Each one it has certain knowledge from logic ICs it is very easy to implement this circuit. For each one he does not have such knowledge, it will be waits for few days until I implement the circuit, and I give the normal drawing. Also because logic circuits it is complicated and unforeseen sometimes, maybe the drawing needs certain small changes. In general from my experience I believe that it will function correctly.
The logic of circuit is separated in three parts. Á) Each time is pressed the up or down button only one relay set and all the others simultaneously reset. B) During the activation of preamplifier a master reset executed to avoid any false of activating two or more relays simultaneously, thus each time the first relay will be activated always. The system it is something between volatile and non-volatile type. C) The circuit is easily expandable to drive any type of indicator of the input selected as I thing so. Let us to see a brief explanation of the logic used. During the supply of preamplifier the 556C reset the up-down counter M74HC192 which may be noted that is the only available in the market with separate count-up and count-down inputs from ST because the only equivalent SN74LS192 of Motorola it is obsolete. It is a decade counter. The 556F serves to keep all the analog switches 4066 activated during reset as the signal can be passing to coils. This procedure it lasts for 5 seconds for certainty. During input selection procedure when the button up or down is pressed, then by triggering the corresponding 556A or 556B monostables which drives his output in high state for 0,5sec this translated from inverter HC04 in low state in the input of counter. For the time of 0,5sec the counter does not change state but after the output of 556A is released and goes in his low state again, this translated from HC04 in a positive going pulse in the input of counter so it counts by one changing the state of his outputs. If the button it is pressed continuously then the 556A or 556B start to operate as a pulse generator causing thus the continuous up or down counting of HC192. Because we have to control 8 relays, when the counter reaches the BCD 8 his output Q3 goes high and then resets the counter which starts again to count from 0. The output code of Q0, Q1, Q2, it drives simultaneously the address inputs of the two decoders HC259 and HC138. The HC138 it is a clear 1 of 8 decoder/demultiplexer while HC259 it is a mixed type IC which can be operate as addressable latch or as memory and as 8 line demultiplexer exactly as HC138. The difference between theme it is that HC138 has negative output logic instead HC259 has positive output logic. We need the two opposite logics for the proper operation of set and reset the relays. It is not possible to I include the truth table because his size. Generally when, let to say, X0 output it is high, X1-X7 outputs are low and in the contrary in HC138 the Y0 out is low and Y1-Y7 outputs are high; and so on. For the momentary transfer (NOT continuous!) of the output state of HC259 and HC138 in the coils mediates the 4 analog switches 4066. These activated in synchronous mode with each count up or count down via the monostable 556D and 556E. The only difference it is that the 556D and 556E when triggered remain in high output state (activating thus the 4066) for 1sec, the double time from the 556A – 556B, thus ensures that the data will be passed with assurance in the coils.
Fotios
An externally hosted image should be here but it was not working when we last tested it.
Nice work Fotios... I was thinking use a PIC... "easy" to add all kinds of fancy switch-on/switch-off sequences...plus benifit of being able to interface with LCD, even manage things like standby/shutdown.
But you seem to be headed down an interesting path....
I suppose one could still monitor the output from the 74hc192 and the 555's with a seperate PIC to provide LCD interface... could even be a seperate module s long as you leave the 4 connection points available....
But you seem to be headed down an interesting path....
I suppose one could still monitor the output from the 74hc192 and the 555's with a seperate PIC to provide LCD interface... could even be a seperate module s long as you leave the 4 connection points available....
The use of latching relays seems like a very good idea. My experience with (non-latching) Nais DS2Y indicates they are quite transparent through the normally closed contact and very unpleasant sounding once energized.
And i have to agree with Nordic that a micro of some kind is the sensible way to control them.
And i have to agree with Nordic that a micro of some kind is the sensible way to control them.
Nordic said:
Hi Nordic
Thanks for your good words. Of course the use of a microcontroler it is by far the most better solution. I have in my bookshelf the MPLAB ICD development system of Microchip for 5 years. As you know it is a suite for prog. - debug. - emul. the familly of PIC16F87xx; the flash type (PIC16F873-876 with 3 set of I/O ports and PIC16F874-877 with 4 1/2 set of I/O ports. But i don't learned yet the RISC language. Instead i have also a ST development system for the familly ST90Rxx which programmed with the assembly language of ST. From this type of assembly i have some experience. Do you know for what reason i don't engaged with PICs? Because they don't offer ready the instruction of multiplying and dividing (instead in ST they offered ready) and thus there is need of extra work for building subroutines. Anyway, i thing yet the smallest members 16F873-876 with the 3 sets of ports are adequate for implementing the logic circuit which i invented. The two set of PortA and PortB for managing relays and the third set of PortC for managing a 4X20 characters LCD display. Unfortunattely i don't have time to spend for programming debbuging etc. a mcu. BTW i thing that a better solution from mcus it is the use of pld. One of my friends has an amazing pld development system of ALTERA which includes in its software an amazing graphical environment in which included all the logic ICs. This circuit can implemented with a such device in 1 to 2 hours! You draw such as in a PCB software and then you place a pld in the socket of programmer and voila!! A ready to use pld. But the price of this system as i remembered it was before 7 years about 3500 euros! By anyway, the implementation of the circuit given in a PIC it is verry easy as i thing. The only difficult it is the programming of the part which drives the LCD. Well my friend, if you are in position for development a PIC with the logic in my draw, a copy of code it is well appreciated from me
because i am this moment.Regards
Fotios
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