Making a 4, 8 and 16 ohm selectable dummy load
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- Опубліковано 24 сер 2024
- What better way to spend a late night than making a quick and easy project. Watch over my shoulder as I make a selectable dummy load used for testing amplifiers and other pieces of equipment. A reasonably quick and easy project only involving a handful of components and some point to point wiring.
Something I don't cover much in the video is the power handling of the finished dummy load. It's certainly not going to be massively high power but will be enough for most lower output amps and could be used at higher powers for short lengths of time. Even though in the 8 and 16 ohm positions the theoretical power handling capacity is 50w actually it will be limited by the switch. Going from the datasheet I think the switch can probably handle about 35w meaning that the final power ratings will be something like this:
4 ohm, 25w
8 ohm, 35w
16 ohm, 35w
Also apologies for the flicker - it wasn't obvious until after it was all filmed, doh! Exposure will be locked next time...
That is very small resistor for a dummy load (25W). It will quickly overheat
This started out great for a novice like myself. Just the thing. Then you got bored and skipped the soldering element. Also what is the selector? Do you have a link to it, maybe? Why have you only made one vid? You obviously have a flair for this sort of thing and could make a few bob. Look at My Mate Vince. Hope you make a few more but actually show what you're doing and not just show the finished product. Thanks for the vid.
Good quality video.... clear picture.... "listenable" voice.... seems quite knowledgeable.... make some more and your views will surely increase.
I'm more interested in testing PSUs rather than amps.... but I'd still watch more of this.
can we use a dummy load resistor to connect a 4ohm speaker to an 8ohm amp by putting the speaker and a 4ohm load resistor in series ?
yes you can
Hello, I just stumbled across this video I doing some research for a dummy load. I was wondering if you have a part number for the rotary switch you are using, as I am having issues finding something suitable.
All of those switches have only two working positions. Three CHEAP rocker DPST switches are enough.
How did you wire the rocker switches to get the correct loads?
@@austinsmith1112 Exactly as @15:19 but they are only on/off. From left to right, 0,1,0> R1 + R2 (16 ohm) __ 0,0,1 > R1(8 ohm)__1,0,1 > R1 || R2 (4 ohm)
Very informative video. Thank you for posting it. When connecting two resistors in parallel or series, how is the wattage affected?
Good question. Resistors in series or parallel share the load evenly if they are all of the same resistance. The resistors I used in this project were 25W so the power handling of both resistors connected in series or parallel is therefore 50W. If there were three equal resistors it would be 75W and so on. If the resistors were different values you would need to do some maths to work out the power going through each resistor. However you also need to think about the power handling of the rest of the circuit, in my case the switch can only handle about 35W so that becomes the limiting factor in the 8 or 16 ohm ranges.
@@jegprodtech4174 Thank you! Will you be posting more videos?
Hi, I will indeed. I have a number of audio and repair projects waiting currently. Sadly I moved house early this year. Disruption from work, moving my whole workshop setup and now Covid-19 havea all hugely delayed my plans!