I am building a circuit simiilar to this, (http://i248.photobucket.com/albums/gg192/gtrplaya101/Relayforeffects-1.jpg) to make true bypass via relays.
I've ready "A remote indicating bypass" on www.geofex.com about a million times. I've never been able to get the "snubbing" portion right. So i breadboarded what's on the circuit in the pic i provided and it works. (Does it pop I don't know)
What i wanna know, is that if the two wires that form the "switch" have a common for me to pigtail several of these circuits together? For instance, i wanna make a 6 loop rackmount looper with each channel sharing this circuit (or close to it),
and I wanna use an 8 conductor ethernet wire to attack the rack to the remote footboard that houses the switches.
I have been making relay based true bypass boxes for a couple years now, but now I wanna get the snubber section proper so My pedals switch silently..
Anyone?
BTW:
The tranny a 3904, the resisters are 4.7k, cap 0.1 ect.
im not sure if i understand you correctly but... you want to make an 8 conductor wire control 6 of these circuits?
yes you can do it
the "common" wire would be the one going to + power "SW1".
sorry if i misread you and thats not what you were asking.
Quote from: slotbot on April 10, 2010, 02:28:04 PM
im not sure if i understand you correctly but... you want to make an 8 conductor wire control 6 of these circuits?
yes you can do it
the "common" wire would be the one going to + power "SW1".
sorry if i misread you and thats not what you were asking.
That is what I'm asking. I guess another snag i wanna get around is having the + be the common between the seperate loops. Though that would be fine in the rack example I mentioned, I am gonna build other units that need the - to be common as to allow a standard t button footswitch with a common sleeve to switch one of these circuits and perhaps change an amp function too, which are usually-. Does this require an npn tranny (assuming this one is pnp) to accomplish?
Also, thanks for replying.
Hi
i think you could do it with NPN and a ground reference.
add a resistor, say maybe 1k, from SW1 to SW2 (collector of NPN to base).
then connect your switch, 1 lug at SW2 and 1 at power - (ground).
connect the switch one lug to power - adn one to the base of the transistor. :icon_confused:
basically what will happen is when the switch is open the relay will be on. when the switch is closed, the base will be grounded and the transistor will turn off, which means the relay will turn off.
try it and see. i thinkit will work though.
Quote from: slotbot on April 10, 2010, 02:45:09 PM
Hi
i think you could do it with NPN and a ground reference.
add a resistor, say maybe 1k, from SW1 to SW2 (collector of NPN to base).
then connect your switch, 1 lug at SW2 and 1 at power - (ground).
basically what will happen is when the switch is open the relay will be on. when the switch is closed, the base will be grounded and the transistor will turn off, which means the relay will turn off.
try it and see. i thinkit will work though.
Nice logic there. I'm new to this end of the spectrum but that really makes sense. I'll breadboard it up and see what happens. I really appreciate you taking the time to help me out.
Rock on!!
Jeremy
This indeed works flawlessly. I haven't hooked up the audio lined to listen to see if the pops are eliminated but I'm onto that next.
Thanks again!!
Jeremy
alright cool.
good luck.
Well, unfortunately for me, I found out too late that i had my wire going to ground on the wrong end of the resister... On both sides it bypasses the relay, but on the one side it also short circuits the power supply, resulting in me frying my trusty Ibanez wallwart I've been using since 1998. Luckily I bought a second recently, but nonetheless a bummer... :icon_cry: The circuit works it seems though, so i'm happy for that!!
oh whoops you are right. the control should not not go to sw2 but the base of the transistor.
sorry about that again. :(
Quote from: slotbot on April 10, 2010, 03:41:55 PM
oh whoops you are right. the control should not not go to sw2 but the base of the transistor.
sorry about that again. :(
Well, it's truly a small price to pay for the knowledge I gained. This has opened up my understanding a bit more which is a great thing.
Thanks!
Well I breadboarded this and the pop is ever present, and this is just using jumpers for the loops rather than pedals, so it's mechanical click. Any ideas?
what are you using for a power supply?
also i would suggest disconnecting the signal ground (from the 'S' inputs) from the power - of the relay circuit and ultimately running the relay power off an isolated power supply from the pedals or whatever is in the signal chain.
Quote from: slotbot on April 10, 2010, 05:44:52 PM
what are you using for a power supply?
also i would suggest disconnecting the signal ground (from the 'S' inputs) from the power - of the relay circuit and ultimately running the relay power off an isolated power supply from the pedals or whatever is in the signal chain.
I will look into keeping the power ground and signal ground isolated. I remember RG mentioning that they could be connected with a 100ohm resistor or left open, whichever is more quiet.
I'm using an Ibanez ac109, and it's always been a great power supply for me, stable 9v all day long. never had noise issues either after many builds.
hmm. well hopefully someone comes along who has actually done this and might have some better insight....
I would suggest trying to disconnect the signal and power grounds. do an experiment just with the send and return jumpered like you were doing.
Quote from: slotbot on April 10, 2010, 06:36:12 PM
hmm. well hopefully someone comes along who has actually done this and might have some better insight....
I would suggest trying to disconnect the signal and power grounds. do an experiment just with the send and return jumpered like you were doing.
So far it seems to be the exact issue with the grounds isolated. I'll have to mess around a bit more. The circuit as is is reported to work, and i even have the same relay as the designer. They originally called for a 470r resistorfrom sw to tranny, but i put a 4.7k instead and it worked. i then realized all my 4.7r are in fact 4.7k. maybe this is my issue?
Quote from: trixdropd on April 10, 2010, 06:50:55 PM
Quote from: slotbot on April 10, 2010, 06:36:12 PM
hmm. well hopefully someone comes along who has actually done this and might have some better insight....
I would suggest trying to disconnect the signal and power grounds. do an experiment just with the send and return jumpered like you were doing.
So far it seems to be the exact issue with the grounds isolated. I'll have to mess around a bit more. The circuit as is is reported to work, and i even have the same relay as the designer. They originally called for a 470r resistorfrom sw to tranny, but i put a 4.7k instead and it worked. i then realized all my 4.7r are in fact 4.7k. maybe this is my issue?
Alright,
I used the circuit snippet with the relay and snubber on rg's Geofex site for the cmos switcher. very simiilar to this circuit. I get the exact same popping regardless of how logic and audio ground are tied together, as well as wether or not I create a ground reference. The circuit physically functions fine, but the pops are still there just as bad as without the r/c network
Bump, anybody else wanna chime in?
There is a capacitance between the relay coil and the signal path. This varies with the mechanical construction of the relay. When the relay coil is switched, the voltage on it necessarily does some very quick movements. You can't totally suppress these voltage changes. I have seen relays in guitar amps with 1uf, as big as 22uF capacitors across the relay coil.
The capacitance to the audio path plus the impedance of the audio path form a high pass filter. The higher the impedance of the audio path, the lower the frequencies this filter lets through.
Slowing down the coil voltage transition lowers the frequencies present in the voltage changes on the coil. It helps and may be enough for some relays.
However, the higher the impedance of the signal path, the worse things are.
There are some relays which shield the contacts from the coil with a grounded shield. This helps a lot, and only degrades the audio with the capacitance to ground of the signal to the shield.
Suppressing relay pop will always be a combination of finding the right relay, slowing down the coil, and shielding the signal path, in some combination.
could you use an RC series circuit in parallel with the coil instead of just a capacitor? this would slow things down quite a bit no?
if you used the right values maybe you could even make a tremolo :)
Quote from: R.G. on April 11, 2010, 05:37:34 PM
There is a capacitance between the relay coil and the signal path. This varies with the mechanical construction of the relay. When the relay coil is switched, the voltage on it necessarily does some very quick movements. You can't totally suppress these voltage changes. I have seen relays in guitar amps with 1uf, as big as 22uF capacitors across the relay coil.
The capacitance to the audio path plus the impedance of the audio path form a high pass filter. The higher the impedance of the audio path, the lower the frequencies this filter lets through.
Slowing down the coil voltage transition lowers the frequencies present in the voltage changes on the coil. It helps and may be enough for some relays.
However, the higher the impedance of the signal path, the worse things are.
There are some relays which shield the contacts from the coil with a grounded shield. This helps a lot, and only degrades the audio with the capacitance to ground of the signal to the shield.
Suppressing relay pop will always be a combination of finding the right relay, slowing down the coil, and shielding the signal path, in some combination.
I messed with the circuit some more. I made the circuit in the schematic in the "A remote indicating Bypass" article. I measure with a meter that indeed the pop is supressed quite a bit. I put a 220uf cap across the coil.
I don't have a 47uf available to test. My relays are hi sensitivity. Are there any values i should experiment with resister wise?
Also, in your circuit RG, does establishing a ground reference and using ground as my common going to be an issue at all?
Quote from: slotbot on April 11, 2010, 07:01:24 PM
could you use an RC series circuit in parallel with the coil instead of just a capacitor?
Yes; however, this has some quirks.
A simple C in parallel with the coil makes for a damped ringing resonant circuit. The coil has a moderate inductance. Some relays even specify the inductance range in their datasheet; it changes depending on relay open or closed. The coil has a non-trivial resistance. Putting a capacitor across the resistor/coil forms a damped RLC circuit. When you put a transient into it, it rings at the natural frequency of the RLC. Putting more resistance in series with the C changes the damping by making the C less effective. The voltage on the coil is less constrained by the capacitance. This ... may ... be a good idea or not, depending on the amount of total damping it introduces. Damping eats energy out of the stored current in the coil as it oscillates back and forth into the capacitor. Prolonged oscillation is not a good thing.
Every RLC circuit reacts to a transient step by producing an initial smaller step plus ringing. You juggle how much of a step versus how much ringing by setting the damping.
Quote
this would slow things down quite a bit no?
No. Imagine that the resistance in series with the cap can be between 0.001 ohm and 1M ohm. At 1M, the capacitor is essentially not even there, and exerts little effect on the inductor. At 0.001 ohm, the resistor is effectively not there. In the middle, the resistor damps things some. But the resistance of the inductor already damps things. The exact value needed for least audibility and fastest relay response depends heavily on the values of R, L and C.
However, the ring frequency of the LC is always determined by the value of L and C. R's have no frequency selectivity.
Quote
if you used the right values maybe you could even make a tremolo :)
?? Not sure how that would work ???
Quote from: trixdropd on April 11, 2010, 08:22:20 PM
I messed with the circuit some more. I made the circuit in the schematic in the "A remote indicating Bypass" article. I measure with a meter that indeed the pop is supressed quite a bit. I put a 220uf cap across the coil.
I don't have a 47uf available to test. My relays are hi sensitivity. Are there any values i should experiment with resister wise?
Without knowing the exact values of the coil inductance and resistance, can't say. What you might try is putting a resistor in parallel with the coil. This eats DC current when you have the relay energized, but also damps the coil a lot when you turn it off. This suppresses the coil's swing, too.
QuoteAlso, in your circuit RG, does establishing a ground reference and using ground as my common going to be an issue at all?
Strictly speaking, there is no need for the relay power to have a common ground with the audio at all. However, you could inject power line hum if you powered the relays from a completely isolated power supply run from the AC mains. What you might do is isolate audio ground and power ground for the relay coils, and connect them through a resistor, then try different resistances. Something between 10 ohms and 1K should let you experiment and get best hum reduction and most isolation.
Quote from: R.G. on April 11, 2010, 08:33:22 PM
Quote from: trixdropd on April 11, 2010, 08:22:20 PM
I messed with the circuit some more. I made the circuit in the schematic in the "A remote indicating Bypass" article. I measure with a meter that indeed the pop is supressed quite a bit. I put a 220uf cap across the coil.
I don't have a 47uf available to test. My relays are hi sensitivity. Are there any values i should experiment with resister wise?
Without knowing the exact values of the coil inductance and resistance, can't say. What you might try is putting a resistor in parallel with the coil. This eats DC current when you have the relay energized, but also damps the coil a lot when you turn it off. This suppresses the coil's swing, too.
QuoteAlso, in your circuit RG, does establishing a ground reference and using ground as my common going to be an issue at all?
Strictly speaking, there is no need for the relay power to have a common ground with the audio at all. However, you could inject power line hum if you powered the relays from a completely isolated power supply run from the AC mains. What you might do is isolate audio ground and power ground for the relay coils, and connect them through a resistor, then try different resistances. Something between 10 ohms and 1K should let you experiment and get best hum reduction and most isolation.
Cool RG, Thank you for the help. I will experiment some more and report back.
Quote?? Not sure how that would work Huh
well i was just making a joke. but really i think you could if you picked nice values. like if you go here
http://www.falstad.com/circuit/
and import
$ 1 5.0E-6 10.20027730826997 46 5.0 43
v 544 112 544 48 0 0 40.0 5.0 0.0 0.0 0.5
w 464 368 544 368 0
w 544 32 544 48 0
r 208 208 208 256 0 10.0
c 208 256 208 368 0 1.4999999999999999E-5 -3.841805128025876E-4
w 208 208 208 176 0
w 208 176 272 176 0
w 208 368 272 368 0
178 144 224 64 224 0 1 1.0 2.4498178926322914E-6 0.05 1000000.0 0.0010 0.1
w 144 256 176 256 0
w 176 256 176 176 0
w 176 176 208 176 0
w 144 272 144 368 0
w 144 368 208 368 0
t 336 128 272 128 0 1 -5.0 4.086786860476207E-4 100.0
w 272 144 272 176 0
r 336 128 336 32 0 100.0
w 544 32 336 32 0
w 272 112 272 32 0
w 272 32 336 32 0
s 336 176 336 272 0 0 false
w 336 128 336 176 0
w 544 272 336 272 0
w 544 368 544 272 0
w 544 112 544 272 0
w 400 368 464 368 0
r 272 368 400 368 0 100.0
x 61 415 602 421 0 24 turn it back on and watch the relay flip on and off.
x 45 458 440 464 0 24 maybe tremolo was the wrong word.
x 367 181 616 185 0 15 turn this switch off and relay goes on...
x 456 451 673 454 0 10 but i was imagining the relay going on and off
x 51 53 103 59 0 24 hello
i was just making a joke though... because you have oscillations (like you mentioned)... maybe to turn the signal on and off... like a tremolo ;D
Just looking at the layout in the first post, it appears the relay has a diode across the coil. The diode is oriented so that it does not conduct unless the coil voltage at the collector of the transistor goes above the supply voltage, so there is no conduction when the relay is on or off in the steady state. When the relay switches off, the coil voltage will go above the supply (sort of like an ignition coil) with an uncontrolled rise until the diode conducts. This delays the opening of the relay because the current in the coil is still flowing in the same direction. I have seen series diodes used for redundancy or in series with resistors to permit the relay to open faster by permitting more voltage drop in the circuit around the snubber.
R-C snubbing draws power during the turn-on whereas a diode does not, so a diode will eliminate the need to size the transistor for the coil current and the capacitor current. A diode will also tend to eliminate ringing, which may be unacceptable in an audio application.
Good luck with the build!