AC millivolt to switch DC relay?

[ScottSlagle]

Hello. Have been trying to swith a 12VDC relay with a low AC signal voltage of between 10-200mVAC. The mV signal is a guitar's output(with passive pickups). The dramatic range of the mV signal, is proportional to the velocity used when strumming the guitar. What would be the simplest way to achieve this? I think the guys at Radio Shack are beginning to point and laugh when they see me coming now.
Thank you in advance for you help.

 

[andre_luis]

Amplify, rectify and filter.

+++

 

[ScottSlagle]

Amplify,rectify, and filter? The first of the three seems to be my biggest hurdle. I've tried experimenting with step up transformers. My output was actually less than my input signal, when wired as a step up transformer, or step down. In hopes of ruling out manufacturer defects, I repeated the experiment with another transformer. Results were the same.
I've tried N channel transistors. Gate voltage being much lower than drain killed that idea.
What would be the best way to amplify the low mVAC signal?

 

[andre_luis]

Transformer is a passive component and doesn´t amplify the power, but voltage.
I was talking about active amplifier.

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[Pjdd]

Scott, I don't want to sound discouraging but it will be well nigh impossible to do what you want to do without some active circuits that may look fairly complex to someone with a limited experience in electronics. Do you care to share what you want to switch with the relay?

 

[ScottSlagle]

Scott, I don't want to sound discouraging but it will be well nigh impossible to do what you want to do without some active circuits that may look fairly complex to someone with a limited experience in electronics. Do you care to share what you want to switch with the relay?

I hope to use the relay to switch channels, in a guitar amplifier. The high gain circuitry of the preamp has a REALLY loud hiss. Switching to the "clean" channel eliminates the hissing.
Voltage measured at the channel selector switch is 12VDC. I would like to use the AC output of the guitar to switch the 12v relay. That way, the amp is switched from the high gain channel automatically, when the guitar is not being played.

 

[pilko]

Try a sound operated/activated switch.--- like this

**broken link removed**

pilko

 

[Pjdd]

Let's see if I've got this right. Is it that you want to stay on the clean channel when you're not playing the guitar and then automatically switch to the high-gain channel (maybe to use some distortion or sustain effects) when you strum it? In any case, do you feel up to constructing circuits using opamps, transistors and the like?

 

[ScottSlagle]

Let's see if I've got this right. Is it that you want to stay on the clean channel when you're not playing the guitar and then automatically switch to the high-gain channel (maybe to use some distortion or sustain effects) when you strum it? In any case, do you feel up to constructing circuits using opamps, transistors and the like?

That correct. I play in the high gain channel 99% of the time. When I stop, silence (clean channel) is the goal.
I welcome the opportunity. What I do not know/understand yet, I will gladly research.

 

[Pjdd]

I don't have any ready design of my own for that nor do I know of any published circuit. I'll see if I can find time to come up with one over the next few days. Can't promise anything, so don't hold your breath.

 

[ScottSlagle]

I don't have any ready design of my own for that nor do I know of any published circuit. I'll see if I can find time to come up with one over the next few days. Can't promise anything, so don't hold your breath.

Not a problem. I thank you for your time

---------- Post added at 15:49 ---------- Previous post was at 15:39 ----------

Try a sound operated/activated switch.--- like this

**broken link removed**

pilko

Hi. Thank you for the response. The idea is brilliant. My only concern is that the same signal that switched the unit on, would also switch it off, as I'm playing? Perhaps I could work some magic with latching relays....

 

[kak111]

I hope to use the relay to switch channels, in a guitar amplifier. The high gain circuitry of the preamp has a REALLY loud hiss. Switching to the "clean" channel eliminates the hissing.
Voltage measured at the channel selector switch is 12VDC. I would like to use the AC output of the guitar to switch the 12v relay. That way, the amp is switched from the high gain channel automatically, when the guitar is not being played.

What is your amplifier model & type ?
Do you use any devices between guitar and amplifier ?
( If Yes : tell models & types )
My opinion is that you need a bit more intelligent solution for this problem.

KAK

 

[ScottSlagle]

What is your amplifier model & type ?
Do you use any devices between guitar and amplifier ?
( If Yes : tell models & types )
My opinion is that you need a bit more intelligent solution for this problem.

KAK

Amp is a B-52 model AT-100. It's an all tube head . The B52 is not the only amp to suffer this issue. It's accepted as being the nature of the beast, in high gain amp's. Most players simply switch channels manually, with a foot controller, before and after playing.
I use no effects between guitar and amp.
There are other "more intelligent solutions" on the market that target the effects loop. Those more intelligent solutions come with their own inherent issues. The price tag is a definite factor. Then, there are often threshold and/or decay issues, depending guitar output and strum velocity.
Perhaps you know of a more intelligent solution? I'd LOVE to hear it. My not so intelligent solution is simply an embellishment of what is normally being done, and has been done for years. That being, switch the channel manually. I move all over when I play. I don't like being anchored to a certain area of the stage, to facilitate a noise free environment, by manually switching channels with my foot controller at the end of a song

 

[mrarslanahmed]

use NPN darlington topologies for amplification......

 

[pilko]

What about a radio controlled remote switch.---transmitter on your guitar-- receiver on your amp. You can buy them for around $20.

pilko

 

[vimalkhanna]

You need the frequency of the 10mV -200mV input signal.
This needs to be 50Hz in order to use a mains transformer .
As such ,it is advisable to use a CAR audio amplifier to amplify from microphone input .
The Loudspeaker output terminal is used to drive any relay with 12VDC coil voltage .