szukalski
Well-known member
I’d just remove U1 from the BoM and not worry about the rotation. It’s something you’d solder yourself.
A simple Relay Bypass
- Thread starter Chuck D. Bones
- Start date
Thanks. Sorry to hijack this thread. I posted in the Troubleshooting forum.
Normally I would prefer to do exactly that but its just that I only have access to FTR-B4CA via Mouser and that's like $4 to $5 whereas if procured from LCSC via JLCPCB assembly, it's like $1. I was thinking of getting 10 to 15 done.
Also, it appears that a slightly cheaper alternative EC2-4.5NU can b used in your circuit but the footprint seems to be different. Anyway, I will try it on a vero and see if the relay switch would actually help in my case.
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Fama
Well-known member
I've built up two of szukalski's Simple Relay Board v1.1's now, which are identical to the original schematic here. Both have an issue where they turn automatically on when I plug in the power - any idea what could be causing that or how to fix it?
I increased C2 to 47nF in the second one because someone mentioned in an another thread it might help, but no dice.
Weirdly enough, I think a lot of other people don't have the same issue. I use a B3CA4 relay.
I increased C2 to 47nF in the second one because someone mentioned in an another thread it might help, but no dice.
Weirdly enough, I think a lot of other people don't have the same issue. I use a B3CA4 relay.
Chuck D. Bones
Circuit Wizard
If it's really that big of a deal, there are a couple of fixes.
One fix involves using the RESET pin to force the 555 into the reset state on power-up. This causes the relay to be energized immediately after power is applied. We also need to rewire the LED so it is OFF when the 555's OUTPUT pin is low.
Now we are faced with two choices:
Rewire the relay contacts so that when the relay is energized, the contacts are in bypass mode.
- OR -
Add a MOSFET to invert the relay drive. We get the added bonus of the MOSFET being able to drive more current than a 555.
The other fix is to change the capacitor values so that the capacitors "encourage" the 555 to power up in the set state. This is a bit of a balancing act because making both caps larger limits how quickly one can cycle the relay. We also have to maintain a large enough difference in the capacitor values for the circuit to work reliably.
Those of us who have tried these fixes prefer door #1, even though it adds 3 or 4 parts (3 for the reset circuit, plus a MOSFET if we go that route).
One fix involves using the RESET pin to force the 555 into the reset state on power-up. This causes the relay to be energized immediately after power is applied. We also need to rewire the LED so it is OFF when the 555's OUTPUT pin is low.
Now we are faced with two choices:
Rewire the relay contacts so that when the relay is energized, the contacts are in bypass mode.
- OR -
Add a MOSFET to invert the relay drive. We get the added bonus of the MOSFET being able to drive more current than a 555.
The other fix is to change the capacitor values so that the capacitors "encourage" the 555 to power up in the set state. This is a bit of a balancing act because making both caps larger limits how quickly one can cycle the relay. We also have to maintain a large enough difference in the capacitor values for the circuit to work reliably.
Those of us who have tried these fixes prefer door #1, even though it adds 3 or 4 parts (3 for the reset circuit, plus a MOSFET if we go that route).
Fama
Well-known member
Oh, so it is a sort of a tradeoff? Bypass on at power on because fixing it would require multiple parts? In that case, I can live with it (or, well, I'm planning to probably sell these off, but I doubt it will be unbearable for the buyer). I wouldn't do all my pedals with these though, because that would get annoying (the way I have my equipment set up I usually power up my pedalboard each morning, although I might change that).
I was under the impression that it's not how this is supposed to work and thus figured there might be a simple fix, but if mine are working as intended, then it's fine. Thanks!
Sturdag Lagernathy
Well-known member
I built a few boards using this schematic, (after paneling I got 15 pcb's inside 100mm x 100mm.. 60 boards for 2 dollars and shipping at JLCPCB!) I changed the contacts on my schematic after noticing the on-at-power up design. I was wondering if there was a reason to do it that way...
P.S. I haven't built up any of these boards yet, did I just make 60 tiny drink coasters?
Fama
Well-known member
FWIW, I noticed the 47nF version did not start on-at-power up when I used an old Boss 9V power supply, but it happens consistently with the bigger power supply on my pedalboard. So YMMV, I guess that's part of the "balancing" approach Chuck mentioned. If you get the caps right for your power supply it won't happen.I built a few boards using this schematic, (after paneling I got 15 pcb's inside 100mm x 100mm.. 60 boards for 2 dollars and shipping at JLCPCB!) I changed the contacts on my schematic after noticing the on-at-power up design. I was wondering if there was a reason to do it that way...
P.S. I haven't built up any of these boards yet, did I just make 60 tiny drink coasters?
No idea what changing the contacts would do, if it's good or bad.
Sturdag Lagernathy
Well-known member
I was just making a dumb joke, changing contacts around shouldn't affect anything, I was really wondering more about the specific design choice!
I used v1.1 schematic BTW..
I used v1.1 schematic BTW..
Brett
Well-known member
This isn't entirely true, at least not reliably (in my experience). I had one circuit using the bypass with 220nF and 47nF caps on the debounce portion that worked super well. I went ahead with those values and ordered a bunch of pre-assembled bypass boards. Those board exhibit the same problem in other circuits.
When it comes to changing cap values, what @Chuck D. Bones said about the responsiveness of the circuit is absolutely true, speaking from personal experience (I am one of the "those of us who have tried" he mentioned). You will end up with larger value caps on the debouncing portion of the circuit and the switch feels less and less responsive with each increase.
If you are having issues with the circuit's state on power-up, use one of Chuck's suggested solutions.
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JonesXavier
New member
Nice! Congrats! I Have 2 relays here, are OMRON G6S-2 4,5 VDCso when i first fired up the circuit it was immediately apparent that my layout (above) had the bypass/active routing backwards (LED on in bypass).
revised layout (for 12V circuit, 520R/9V coil):
View attachment 57902
verified
View attachment 57901
fitted it to a CE-2 build running @ 12V. was quite a squeeze.
but it works!
it's an awesome switch. i love it.
thanks for sharing this circuit @Chuck D. Bones
I looked for this information in the datasheets but I didn't know how to interpret it. Do you know if I can use this Omron G6s-2 relay in this layout you posted? Or some appropriate layout? The ones I've tried so far have had a very loud pop! Thank you very much for your attention! Brazilian greetings!
Chuck D. Bones
Circuit Wizard
That relay will draw 31mA coil current, which is pushing the limits of the 555's drive capability if you power the 555 from 5V. You get a little bit of margin if you power the 555 with 9V. Or you could go with the MOSFET drive option, then you have no issues driving the relay. Omron says the coil is polarity-sensitive, so make sure pin 1 goes to the +5V rail.
I do not know why you are getting a loud pop, that is not normal. Is the pop sound coming from your speaker or from the relay itself?
I do not know why you are getting a loud pop, that is not normal. Is the pop sound coming from your speaker or from the relay itself?
owlexifry
Well-known member
as @Chuck D. Bones has pointed out, it appears this relay is polarity sensitive.
unfortunately it doesn’t look like this relay will work with this layout because the + supply will end up on pin 12 instead of pin 1.
aquataur
Member
I noticed that all of those relay bypass circuits uses a shottky diode in parallel to the relay coil to tame the kickback voltage.
Somebody further up mentioned that he experienced a lag upon relay turn-off, which could well be attributed to a shottky diode.
I had recently done a circuit with a fairly big contactor, which I had fitted with the usual flyback diode (a 1N4007), and the thing just would not turn off in time (upon hitting the end stop switch). I found out this way, that this kind of protection is hardly ever used in current systems. The reason is that there is (in large contactors) a huge energy charge stored in the activation coil, which has to be destroyed in order to remove the charge. Logically, if the voltage is clamped to 0.7V, the charge can only be removed slowly.
This will apply to a small relay only to a smaller extent, but it does, and we do not know what the OP has used.
On some of my builds, like on a speaker turn-on delay and protection, I want the relay to shut off as quick as possible, so I use a (reverse) diode with a 12V Zener in series. If I monitor the mains failing, such a relay turns off before the mains switch can make a pop in the power amp. This makes a remarkable difference in turn-off speed.
Again, this may be an overkill for such a small relay, but using a shottky diode that clamps at 0.25V is not justified. Nothing is endangered with 0.7V of reverse voltage. Unless there were some other reason I fail to recognize.
BTW for the above contactor system I finally used a 50V MOV, and this shuts down the contactor lightning fast.
Somebody further up mentioned that he experienced a lag upon relay turn-off, which could well be attributed to a shottky diode.
I had recently done a circuit with a fairly big contactor, which I had fitted with the usual flyback diode (a 1N4007), and the thing just would not turn off in time (upon hitting the end stop switch). I found out this way, that this kind of protection is hardly ever used in current systems. The reason is that there is (in large contactors) a huge energy charge stored in the activation coil, which has to be destroyed in order to remove the charge. Logically, if the voltage is clamped to 0.7V, the charge can only be removed slowly.
This will apply to a small relay only to a smaller extent, but it does, and we do not know what the OP has used.
On some of my builds, like on a speaker turn-on delay and protection, I want the relay to shut off as quick as possible, so I use a (reverse) diode with a 12V Zener in series. If I monitor the mains failing, such a relay turns off before the mains switch can make a pop in the power amp. This makes a remarkable difference in turn-off speed.
Again, this may be an overkill for such a small relay, but using a shottky diode that clamps at 0.25V is not justified. Nothing is endangered with 0.7V of reverse voltage. Unless there were some other reason I fail to recognize.
BTW for the above contactor system I finally used a 50V MOV, and this shuts down the contactor lightning fast.
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Chuck D. Bones
Circuit Wizard
It's true that the time to unload the energy stored in an inductor, in this case the relay coil, is inversely proportional to the coil voltage. With large inductors, this is a real problem*. The relay datasheets usually don't specify coil inductance, so I measured a couple. An EA2-5NU relay coil measured 184Ω + 35mH. An AS5W-K measured 175Ω + 47mH. The current in an inductor is related to voltage & inductance by:
V = L * di/dt
Where di/dt is the current rate of change in Amps/second.
At 5V, the nominal coil current is 28mA.
Rearranging the equation,
di/dt = V/L
If we clamp the coil voltage at 0.2V with a 2N5817, when we turn the relay off, the coil current will drop at a rate of 4.25 A/s or 4.25mA/ms. The relay will drop out somewhere around 20% of the nominal coil current, in this case around 5.6mA.
It will take 5.3ms for the coil current to drop from 28mA to 5.6mA. This is comparable to the time it takes the armature to move if the current were to drop to zero instantaneously. I think this is plenty fast for a pedal.
BTW, the lag was caused by the time it took for the "memory" capacitor to recharge. We adjusted the Rs & Cs to bring this down to under 200ms.
* I once had a job working on a large physics experiment that included a superconducting magnet. The inductance was about 11H. The operating coil current was 2000 Amps. It took about 1/2 hr to ramp the current up to 2000A. The magnetic field could stop a mechanical watch and erase the magnetic strip on a credit card at a distance of a few m.
V = L * di/dt
Where di/dt is the current rate of change in Amps/second.
At 5V, the nominal coil current is 28mA.
Rearranging the equation,
di/dt = V/L
If we clamp the coil voltage at 0.2V with a 2N5817, when we turn the relay off, the coil current will drop at a rate of 4.25 A/s or 4.25mA/ms. The relay will drop out somewhere around 20% of the nominal coil current, in this case around 5.6mA.
It will take 5.3ms for the coil current to drop from 28mA to 5.6mA. This is comparable to the time it takes the armature to move if the current were to drop to zero instantaneously. I think this is plenty fast for a pedal.
BTW, the lag was caused by the time it took for the "memory" capacitor to recharge. We adjusted the Rs & Cs to bring this down to under 200ms.
* I once had a job working on a large physics experiment that included a superconducting magnet. The inductance was about 11H. The operating coil current was 2000 Amps. It took about 1/2 hr to ramp the current up to 2000A. The magnetic field could stop a mechanical watch and erase the magnetic strip on a credit card at a distance of a few m.
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Silver Blues
Well-known member
Yeah those large superconducting solenoids are no joke. We have an instrument in my lab like this as well, there is enough stray field that when the magnet is charged to maximum field (7 T, I don't remember the exact current needed but probably in the 100s of amps) my (quartz) analog watch(es) stop within a few m of the magnet and you can't have any ferrous metal tools anywhere in the vicinity...
Chuck D. Bones
Circuit Wizard
A 1N4148 will also suffice.
aquataur
Member
Just for the record...
I had used a similar circuit in the vicinity of a coil in the audio path (a wah). Using an OMRON G5V-2 seemed to induce a spike into the coil, and I had to resort to all sorts of trickery to bring this down to a palatable level.
I got hold of a box of NAIS (= Panasonic, Matsushita) DS2E-S DC5V relays and tried this one with a series resistor.
For some reason, they are totally quiet. They are supposedly top quality, albeit not as minute as the ones mentioned here, but then not much bigger than the G6-S2 above.
I had used a similar circuit in the vicinity of a coil in the audio path (a wah). Using an OMRON G5V-2 seemed to induce a spike into the coil, and I had to resort to all sorts of trickery to bring this down to a palatable level.
I got hold of a box of NAIS (= Panasonic, Matsushita) DS2E-S DC5V relays and tried this one with a series resistor.
For some reason, they are totally quiet. They are supposedly top quality, albeit not as minute as the ones mentioned here, but then not much bigger than the G6-S2 above.