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Need help building a relay that will switch on my subwoofer.

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GenoM

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I got a Rotel RSX 1055 AV receiver with a couple of 12V trigger outputs. I would like to use one of them to switch on my sub's amp. The sub has a Hypex 200 amp build in which delivers 100 W into 8 ohms. AC current where I live is 220 Volts.

Although the amp has a sensor input that detects bass signals, it reacts too slow or sometimes doesn't come on at all. There's a three way power switch on the amp I-on; 0-off; II-Standby=sensor enabled.

Unfortunately, Rotel's manual doesn't say what the 12V trigger output does when switching on the receiver. So I need to know how to build a relay that can replace my sub's power switch and uses the receiver's trigger signal. Can anyone give me some pointers? Thanks a million!
 

Gene

New Member
Perhaps the lack of responses is due to a little misunderstanding about what you want to happen and when.

1. What is the voltage/current requirement of your bass booster amp?

2. If you saying that you want the bass booster amp to come on automatically when you turn on your main unit, you should consider what is available at the main amp. Is there a switched mains output? Most amps/receivers have AC jacks offering switched (on when the unit is on) and non-switched (always on) jacks. If not, then what about those 12 volt jacks? Are they AC or DC - - - switched or unswitched?
 

GenoM

New Member
Thanks Chippie. Looks a bit too complex for what I'm wanting to do, but thanks anyway. It sure points in the right direction.

Gene, I'm sorry if I made my story confusing; I'll try to explain. My AV receiver doesn't have a switched 220V output. For what I'm looking for it would make a simple solution for switching on my sub, you're quite right in saying that.

The 12V trigger outputs are a common feature on most high quality AV receivers. They are designed to remotely operate other amplifiers or electrically driven equipment. One much used option is to operate a motor driven projection screen. As I gather, the 12V trigger output sends out a 12V DC signal whenever the receiver is switched on. The signal is detected by a sensing circuit within the remote equipment which in turn activates a relay. The relay switches on the screen motor and the screen travels down, ready for viewing.

In my case, I would want to power up my sub instead of a screen. My sub has a switch which has to be manually engaged for the sub to operate. I would like to replace that switch with a relay. The relay should switch on my sub whenever it receives a 12V trigger input from my AV receiver. In my previous post I assumed 12V trigger outputs on AV receivers were common knowledge among electronic enthusiasts. Hope this clarifies things a bit. Thanks guys!
 

Chippie

Member
I've simplified the circuit for you, this should do for what you require......
Obviously the relay will need to have a 12v coil and suitably rated contacts for the sub woofer full load current, the transformer isnt critical, the secondary needs to provide sufficient current and voltage to energise the relay, 9v ac should be ok, make sure the primary suits your local supply. Make R1 around 10k and R2 somewhere around 1-2k.....Play around with the values such that the circuit switches as you add/remove the control signal.

the diodes are 1N400 series and the capacitor around 470mfd with a rating of around 16-25v dc......

Have fun but do be careful
 

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GenoM

New Member
:roll: Wow.....I'm speechless.......Thank you very much! That's very helpfull of you.

May I ask why manufacturers use an opto couplers instead of a transformer? It was mentioned in the article you showed me and also, Rotel mentions this as a device they use in their sensing circuits on their amplifiers. Should I use an opto coupler? I'm very finicky about my equipment and prefer the best solution without going overboard :) Like to hear from you.

Thanks again!
 

Chippie

Member
The opto-coupler will provide galvanic isolation between the eqpt and the switching unit.......


The led side is illuminated using the control signal, you will need to calculate the resistor value to determine the appropriate current for the led. connect the transistor side to the base circuit of the transistor in the switching unit.....again you may need to play around with r values.....


Best of luck! :lol:
 

Gene

New Member
Sounds like you need a switched 220 line for your booster amp. If I understand you, the 12vdc is a switched output - possibly switched from a remote control. So, when you want it - you get 12vdc. How 'bout this?
 

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GenoM

New Member
First of all let me thank you guys for your help.

Gene: I think Chippie has the correct solution because he uses a circuit that employs the 12V signal as a trigger signal. (Which it is) I'm not a big electronics buff, but from what I understand about trigger signals is that they're usually too low in current to supply continuos power to operate a relay.

Chippie: From what I can read from your schematic, it uses a transformer to supply the power to the relay and a circuit with a transistor that uses the incoming trigger signal to activate the relay. Am I correct?

Now I need to contact Rotel and find out if they have some pointers as well.

Thanks again guys!
 

Gene

New Member
When you contact the manufacturer you might want to discuss the 12 volt output. It could be anywhere from enough to 'trigger' a 12 volt screen motor to a few milliamps. I would have expected the output rating to be labeled on the amp jack.
 

Chippie

Member
GenoM said:
Chippie: From what I can read from your schematic, it uses a transformer to supply the power to the relay and a circuit with a transistor that uses the incoming trigger signal to activate the relay. Am I correct?


Thanks again guys!
Yes, The transformer is there to provide power for the relay etc....
 
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