Trouble trying to make my homemade subwoofer wireless

Thread Starter

objecttothis

Joined Jan 18, 2020
6
Background: I put together a homemade subwoofer using an old monoblock car amplifier (12VDC 300W), 1.5 Farad Capacitor (inline between the power supply and the amplifier and power supply) and a 600W ATX Computer power supply. I modified the power supply by wiring in a SPST rocker switch, cutting off all the connectors and wiring together all of the ground and all of the 12VDC+ wires which are connected to the amplifiers respective ground and 12VDC+ terminals. This setup has worked great for me, but now I want to take the whole thing wireless so that I can control it from my Harmony Universal Remote.

My Solution: I purchased the following IR receiver/relay setup on Amazon (https://www.amazon.com/gp/product/B06XHHNG65/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1).

The Problem: I am not a professional electronics engineer. The relay is marked as 10A 250VAC, 10A 125VAC, 10A 30VDC, 10A 28VDC. Since the Amp is rated for 300W, I think that means it can draw a maximum of 25A. Am I correct in my understanding that this switch will not be able to handle more than 10A? If this is true, can someone point me to (a link maybe) a relay that I can slap on this board after de-soldering the existing relay? Would that work... if I de-soldered the 10A relay and soldered in a 30A relay capable of handling 12VDC?

A side question is whether I even need the inline 1.5 Farad capacitor. I used this when the setup was installed in my car, but I'm not sure, but I'm wondering if given that I'm using a computer power supply and not a car battery that maybe I can just remove the capacitor.
 

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crutschow

Joined Mar 14, 2008
24,352
It's not clear what you are trying to do.
All you need to switch is the AC power to the sub, and a 10A rating should be more than sufficient for that.
 

Thread Starter

objecttothis

Joined Jan 18, 2020
6
I'm sorry it's not clear. Let me try to clarify:

Goal: Turn the subwoofer on and off via IR remote control.

So, are you saying that the relay isn't bearing the entire load of the amplifier, but instead just bearing the load of turning the AC Power supply on or off? That makes sense that it would be far less than 10A.

What is a little unclear to me is exactly how I need to wire this up. The power supply activates when the green wire is connected to ground, so right now that's connected as GND --> SPST Rocker Switch --> Green Wire. The Rocker switch completes the circuit and the power supply delivers power to the Amplifier.

What I want is that when the rocker switch is on, that the IR relay is powered but that the power supply not be powered until the relay is triggered. If the power supply was triggered by positive, I think I would then connect 12VDC+ to COM on the left side and my trigger wire to NO on the left side. Yet, my power supply is negative triggered (Green to GND), so can I just connect GND to COM and the green wire to NO on the left side?
 

crutschow

Joined Mar 14, 2008
24,352
What I want is that when the rocker switch is on, that the IR relay is powered but that the power supply not be powered until the relay is triggered. If the power supply was triggered by positive,
Seems like you need a separate supply for the IR relay, because you don't want the power supply powered until the relay is closed.
You could use a wall-wort type supply just for the relay, and then use the relay to apply AC power to the sub supply.
 

Thread Starter

objecttothis

Joined Jan 18, 2020
6
Seems like you need a separate supply for the IR relay, because you don't want the power supply powered until the relay is closed.
You could use a wall-wort type supply just for the relay, and then use the relay to apply AC power to the sub supply.
OK, I think I may have something. The ATX power supply does not have standby +12VDC, but it does have standby +5VDC on a purple wire. Could I use a boost converter (https://www.amazon.com/KNACRO-Converter-Waterproof-Regulator-Transformer/dp/B01HB6JCN6/ref=sr_1_7?keywords=5v+to+12v+"step+up"+converter&qid=1579379082&sr=8-7) to give me my "always on" +12VDC to power the relay? The Amazon site for the relay that I have lists the working current as "1mA(static), 80mA(relay close)" which I would think that the step up converter could handle with ease.

If that resolves the powering of the relay issue, then am I correct in my understanding that I just need to connect my ground to common and NO to the green wire on the relay side of the PCB?
 

crutschow

Joined Mar 14, 2008
24,352
If that resolves the powering of the relay issue, then am I correct in my understanding that I just need to connect my ground to common and NO to the green wire on the relay side of the PCB?
That should work okay.
Just about any boost converter should work for that.
The relay contacts then carry the low current of the ON terminal of the ATX supply.
 

Thread Starter

objecttothis

Joined Jan 18, 2020
6
Yes, agreed. The problem is that the only 5VDC driven IR board I can find on Amazon doesn't have great reviews and is an IR learning version that I don't really want to deal with. I'll pick up the step-up converter and go that route.

The only other question I have is whether I still need the 1.5 Farad capacitor, or if the power supply can deliver consistently smooth power to the amplifier without it.
 

Thread Starter

objecttothis

Joined Jan 18, 2020
6
By "test by experiment" do you mean to pull the capacitor and listen for the subwoofer cutting out on heavy bass lines or is there a more exact experiment you had in mind?
 
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