You probably shouldn't run your relays on the edge of switching. You pick 12V relays because you expect to have 12V for its coils. Bigger C after rectifier or bigger VAC transformator.
I don't really know how much the 555 cares about a stable power supply, neither do I know if it needs special coupling on any of its pins. Usually ICs want a ~100nF coupling cap near the Vcc pin.
Why not just go for the 7812 regulator + higher VAC transformator?
As to why your main's voltage drops I have no idea. Sounds spooky.
Sorry if I couldn't help.
I don't really know how much the 555 cares about a stable power supply, neither do I know if it needs special coupling on any of its pins. Usually ICs want a ~100nF coupling cap near the Vcc pin.
Why not just go for the 7812 regulator + higher VAC transformator?
As to why your main's voltage drops I have no idea. Sounds spooky.
Sorry if I couldn't help.
All mains will sag somewhat when you power up a big amp. Sometimes, even the lights will dim in the same room.
A much bigger cap will be needed in the timer circuit just to keep the output voltage above the relay operate voltage while the mains are sagging.
As for the size of the cap, I cannot say for sure what will be needed. It is likely that anything small is going to cause chatter because the time constant of the RC network will be too low -- the RC network being made up of the relay coils and the timer power supply capacitor.
The thermistors are 5R, 20 A, which don't even get warm. I might have to get a 12 VAC transformer, just to use the regulator. That too will help through the sagging period.
What bothers me most, is that after all has stabilized, and the lightbulb is dark, the mains are at 114 --- they started at 121 or so.....
A much bigger cap will be needed in the timer circuit just to keep the output voltage above the relay operate voltage while the mains are sagging.
As for the size of the cap, I cannot say for sure what will be needed. It is likely that anything small is going to cause chatter because the time constant of the RC network will be too low -- the RC network being made up of the relay coils and the timer power supply capacitor.
The thermistors are 5R, 20 A, which don't even get warm. I might have to get a 12 VAC transformer, just to use the regulator. That too will help through the sagging period.
What bothers me most, is that after all has stabilized, and the lightbulb is dark, the mains are at 114 --- they started at 121 or so.....
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There is a voltage sag from which there is no recovery even when the suspected caps are removed.
This does not seem right. If the paralleled secondaries were wired out of polarity, the sag would occur before the cap bank was switched in. It happens only when the cap bank is switched in. Then it does not recover.
I tried it with a partial cap bank (1/4 of the overall capacitance) and the relay controller stayed above the "must operate" voltage after the chattering stopped.
That's just secondary -> relay -> diode bridge -> relay -> cap bank. No thermistors involved. Mains still drop 2-3 VAC.
Is this normal?
This does not seem right. If the paralleled secondaries were wired out of polarity, the sag would occur before the cap bank was switched in. It happens only when the cap bank is switched in. Then it does not recover.
I tried it with a partial cap bank (1/4 of the overall capacitance) and the relay controller stayed above the "must operate" voltage after the chattering stopped.
That's just secondary -> relay -> diode bridge -> relay -> cap bank. No thermistors involved. Mains still drop 2-3 VAC.
Is this normal?
OK, first things first.... since the relays are chattering, the power supply voltage will be increased to 12 VAC, a forward biased diode and a 15 volt zener diode will be added to protect the 555 timer ( Vcc max is 18 volts ), and a 12 volt zener on the output of the timer circuit to the coils. (may not be needed).
Since the relays do not currently hold, the mains sag must be so deep that the must release voltage is being met by the timer circuit. Hopefully, this voltage will not be met by the higher voltage transformer.
Since the relays do not currently hold, the mains sag must be so deep that the must release voltage is being met by the timer circuit. Hopefully, this voltage will not be met by the higher voltage transformer.
Just a guess, it's the impedance ratio between the transformer and soft start resistors, the resistors drop a lot of voltage because there is no load on transformer.
by wiring a dual 115V primary transformer with primaries in series on 115V mains.
The drop in the mains voltage was an effect of the light bulb tester power cable. Plugging directly into the wall caused the relays to click once to feed power through the thermistor, and a second time to bypass that thermistor.
Relay coil voltages are now over 10 V.
So there's the rule: Once the light bulb tester shows no shorts, stop using it.
Relay coil voltages are now over 10 V.
So there's the rule: Once the light bulb tester shows no shorts, stop using it.
I just checked the Toronto Hydro "normal operating ranges". They claim that 110 to 125 VAC is normal operating conditions. 110 VAC is too low for the relays to function properly with a 9 VAC transformer.
You are correct AndrewT, a 12 VAC relay is necessary, as is some sort of protection for the 555 timer and relay coils against over voltage.
You are correct AndrewT, a 12 VAC relay is necessary, as is some sort of protection for the 555 timer and relay coils against over voltage.
hello again
still struggling with my choke input F5T:
what is acceptable offset during startup sequence and how fast should the offset settle under 10mV
I know it depends, but mine starts in the region of 200mV, spends 1min to reach below 100 and another to reach below 60, when amp bias is around 290mV on its way to 350 target
offset measured during shutdown flashes above 4-500mV before it drops fast
not to good for compression drivers.....
best
Leif
still struggling with my choke input F5T:
what is acceptable offset during startup sequence and how fast should the offset settle under 10mV
I know it depends, but mine starts in the region of 200mV, spends 1min to reach below 100 and another to reach below 60, when amp bias is around 290mV on its way to 350 target
offset measured during shutdown flashes above 4-500mV before it drops fast
not to good for compression drivers.....
best
Leif