DC power extension


 

Bryan Mayland

TVWBB Hall of Fame
Longer wires are more prone to noise, power supply ripple, and there's a little extra voltage drop along the wire which means the blower will run a little lower speed. That said, I don't think there will be an issue with using it considering it already has a 6ft cord on it and the gauge of that wire is much thicker than the 6ft of the Triad (24AWG). There will be degraded performance but I don't believe it will present any practical issue. Someone here might have already tried it though because the most I've run is about 10ft total.
 

GrantT

TVWBB Member
Looks like they suggest a 2A power supply, so using that and a 12' 20AWG cable at 2A as the current draw, you will lose roughly 0.5 volts at the other end to loss in the additional cable. If the current draw is lower, there will be lower loss.

Their own supplied cable is 24AWG at 6', which at 2A will also drop 0.6 volts at the end.

So, looks like if you string both in series at the maximum of 2A, you will likely see an almost 1V drop by the other end. It all likelihood, the current will be lower during operation and the voltage drop not as significant.

Basic Voltage Drop Law​

Vdrop = IR

where:
I : the current through the object, measured in amperes
R : the resistance of the wires, measured in ohms

So, for example, if you are actually only drawing 0.5A during operation, the voltage drop will only be in the area of 0.3 Volts...probably good to go.

I would do some test measurements to see what voltage you are ACTUALLY seeing on the end of the factory plug NO load, and then with load (you can then figure out the actual current draw - even easier if you have a clamp meter)....dropping 1V in total may be problematic....depends on the actual need of the HM, and if the supply is actually putting out 12V, or something higher (or lower). Running a device on too low a voltage can damage it...

Some devices will specify a RANGE of acceptable voltages and most usually have some play as well.
 
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J Halvo

TVWBB Member
Awesome details, thanks folks. Side related question... if instead of using the A/C PSU I just used a 12V battery (either the one WBegg uses or the scooter one Bryan likes), does that change anything? I presume the voltage loss concerns are the same but is the added noise still in play?

I'll pull out my multimeter in the meantime and check out the stuff from above.
 

GrantT

TVWBB Member
Volts is pretty well volts....either the AC converted or from a battery. The end result on the wire should be pretty much the same...unless the AC-->DC device is putting out something wonky instead of a pure clean DC.
 

Bryan Mayland

TVWBB Hall of Fame
I actually find the noise to be greatly diminished when running off a 12V battery. Even though the AC to DC power adapter is isolated, it somehow picks up more ground noise when it is present. Like if I use HeaterMeter in the toaster oven, if the probe touches the metal of the oven it picks up line noise. That doesn't happen when running on the battery. The voltage of a battery tends to be higher as well so the voltage drop is less of a concern.
 

GrantT

TVWBB Member
Makes perfect sense....an AC adapter, unless it has some good noise filter circuits designed into it, will allow any noise bouncing around the AC wires onto the DC output. Really just acts like a big antenna. A poor AC adapter may even likely ADD to the noise.
 

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