Hello folks.
I'm looking for a simple schematic for specific functionality.
I'm going to use a relay to mute my pre output when turning off (ASAP) and when powering on (mute for a short while).
Could you tell me how to do it?
Relay will be powered from 5V supply.
Thank you for time and effort.
I'm looking for a simple schematic for specific functionality.
I'm going to use a relay to mute my pre output when turning off (ASAP) and when powering on (mute for a short while).
Could you tell me how to do it?
Relay will be powered from 5V supply.
Thank you for time and effort.
use a relay with a timed delay and instant off.
Very similar to a speaker protection relay, only smaller with signal rated contacts.
The output resistor of the pre feeds into the normally closed contact of the relay.
the com is active immediately and shorts the output to audio ground. When the relay triggers the signal passes and is only affected by the small capacitance of the now open contact.
The pre and the output resistor need to be rated to operate in the mute condition.
Very similar to a speaker protection relay, only smaller with signal rated contacts.
The output resistor of the pre feeds into the normally closed contact of the relay.
the com is active immediately and shorts the output to audio ground. When the relay triggers the signal passes and is only affected by the small capacitance of the now open contact.
The pre and the output resistor need to be rated to operate in the mute condition.
As Andrew says, simply use a relay to short the pre output at all except when the preamp is on.
This is about as simple as it gets. If you had a slightly higher supply voltage then we could have used a single FET and simplified it even more. This will work though. Alter the cap to give the delay needed.
This is about as simple as it gets. If you had a slightly higher supply voltage then we could have used a single FET and simplified it even more. This will work though. Alter the cap to give the delay needed.
Attachments
R2 @ 1k allows about 4mA of base current into Q2.
For saturated Q2 that limits the relay current to ~40mA.
What is the specified relay coil current for a 5V signal relay?
R1=470k limits the base current into Q1 to <8.5uA
That is going to make Q2's switching action rather slow, or maybe not switch at all.
hFE = 4mA/8.5uA = 470
that is a very high gain requirement for Q1 and it relies on C1 not sucking out some of that 8.5uA
Is there a higher voltage auxiliary supply inside somewhere?
For saturated Q2 that limits the relay current to ~40mA.
What is the specified relay coil current for a 5V signal relay?
R1=470k limits the base current into Q1 to <8.5uA
That is going to make Q2's switching action rather slow, or maybe not switch at all.
hFE = 4mA/8.5uA = 470
that is a very high gain requirement for Q1 and it relies on C1 not sucking out some of that 8.5uA
Is there a higher voltage auxiliary supply inside somewhere?
I saw something like this.
Could you tell me what do you think about it?
R9 and R10 are 100K.
R11 is 10ohm.
Relay is powered from 12V in this circuit.
I'm not sure about diode (maybe it's Zener) I saw that circuit on some DIYINHK headamp boards.
Could you tell me what do you think about it?
R9 and R10 are 100K.
R11 is 10ohm.
Relay is powered from 12V in this circuit.
I'm not sure about diode (maybe it's Zener) I saw that circuit on some DIYINHK headamp boards.
Its very flexible and tweakable. The 470k and timing cap can easily be altered to suit, say 100k and 82 or 100uf. That would give 2.5 to 3 seconds delay.
I would have to see the exact circuit 🙂
In your drawing, the transistor is PNP which means that the emitter must be positive with respect to the collector. The emitter shows as going to ground though.
If the 12 volts did feed in at that point then the relay still has nowhere for its coil current to flow because D1 would be the 'wrong way' round.
There are to many inconsistencies for it to work I'm afraid, no matter how much you try and account for any individual errors.
In your drawing, the transistor is PNP which means that the emitter must be positive with respect to the collector. The emitter shows as going to ground though.
If the 12 volts did feed in at that point then the relay still has nowhere for its coil current to flow because D1 would be the 'wrong way' round.
There are to many inconsistencies for it to work I'm afraid, no matter how much you try and account for any individual errors.
Because Im unsure what of transistor (or maybe something diffrent) is used.
So there is a picture above.
There is only six elements + relay, nothing more.
And I knot it's working (I mean that circuit).
Circuit is power via 12V and there nothing more than GND and 12V there (no MCU etc).
So there is a picture above.
There is only six elements + relay, nothing more.
And I knot it's working (I mean that circuit).
Circuit is power via 12V and there nothing more than GND and 12V there (no MCU etc).
This is based on your example. It works, but look how much bigger the cap needs to be than in the two transistor example. The one in your picture could well use an FET which would be the best solution but its not workable with a 5 volt supply unless you used very specific parts that might be hard to get.
Attachments
As you can see here :
There is a ground trace comming to capacitor, and 12V comming for diode and 10ohm resistor.
There is a header between that two traces for push-pull button for manual cut-off.
That circuit does not need any external signal/additional circuit to work 🙂
There is a ground trace comming to capacitor, and 12V comming for diode and 10ohm resistor.
There is a header between that two traces for push-pull button for manual cut-off.
That circuit does not need any external signal/additional circuit to work 🙂
Yes, the circuit in the pictures I'm sure works OK, but your circuit diagram in post #5 can not. You have no 12 volt supply shown, and anywhere on that diagram that you introduce 12 volts will not operate the relay. Its all wrong 🙂 do you see ?
I see your point.
I just named 12V trace as a relay 😉
I hope you understand 😀
@Mooly, I assume that your circuit is the easiest and more reliable for that job?
I just named 12V trace as a relay 😉
I hope you understand 😀
@Mooly, I assume that your circuit is the easiest and more reliable for that job?
The one with two transistors is the most repeatable and allows the use of small value caps. The single transistor version needs a large cap and relatively low value resistor (to be able to drive the single transistor) and has the disadvantage (as does the other but not as bad) of only 'using' or allowing the cap to charge to around 0.6 volts before the relay operates. The two transistor one gets that up to around 1.2 volts, so considerably better.
Alright.
If I need 2 sec delay which cap value would be best?
BTW I assume that circuit will give immediate cutoff after powering off my device?
Your circuit is designed for two relays, I assume that I can ommit everything after D4 diode (including it too).
And last one (maybe a stupid question) may I use that circuit for low power relay? I mean that with ultra low power consumption (like 50mW for 5V), typical relay will need more, like a ~ 140mW.
If I need 2 sec delay which cap value would be best?
BTW I assume that circuit will give immediate cutoff after powering off my device?
Your circuit is designed for two relays, I assume that I can ommit everything after D4 diode (including it too).
And last one (maybe a stupid question) may I use that circuit for low power relay? I mean that with ultra low power consumption (like 50mW for 5V), typical relay will need more, like a ~ 140mW.
If we go with Andrews concerns and reduce R1 to 100k to allow for lower gain transistors, then somewhere in the 68uf or 82uf range would give two seconds. If that was a little long then use a 47uf, if you wanted longer then a 100uf and so on. Its very flexible.
I'll look in again later today if you have any more questions 🙂
You can see the delay here. Its about 2 to 2.5 seconds for the values shown.
I'll look in again later today if you have any more questions 🙂
You can see the delay here. Its about 2 to 2.5 seconds for the values shown.
Attachments
I assume there is nothing to worry about when using low power relays ?
I mean this one :
http://www.mouser.com/ds/2/212/KEM_R7003_ED2_EF2-780771.pdf
I mean this one :
http://www.mouser.com/ds/2/212/KEM_R7003_ED2_EF2-780771.pdf
The diode across the resistor helps with the switch off. A lot depends how quickly the rails collapse though.
Remember there are two versions of the circuit shown in my diagram. I'm referring now to the one on the left that uses two transistors. Yes, a low power relay is fine.
BTW Mooly.
If I'm going to use your circuit for higher voltage eg. 12V or 18V should I change something? OFC I know I should replace cap for higher voltage rating and relay 😉
But should I change something more?
If I'm going to use your circuit for higher voltage eg. 12V or 18V should I change something? OFC I know I should replace cap for higher voltage rating and relay 😉
But should I change something more?