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-   -   Modded PC power supply for charging (https://www.rc-monster.com/forum/showthread.php?t=3962)

mvalentine6 06.06.2007 08:11 PM

I have a question what if you want to just use the 5v side do you still need the resistors? I already have a power supply for my chargers and what not but I want to run my lathe,tire warmers without using a battery or my charger.

MTBikerTim 09.23.2007 10:09 PM

I just thought I would add this. It might have already been stated. To load the PSU I just plugged in an old CD drive. Worked really well. I already had a 12v power source but wanted a second one and I discovered the PSU worked a lot better then my dedicated 12v power source. I no longer got false peaks when charging.

And it does depend on the PSU as to whether you will need to load the 5v or 3.3v line. from experience I have found I have only had to put load on the 5v line. But that was on 3 very similar psu.

BrianG 09.23.2007 10:31 PM

That makes sense. A CD drive uses 5v and 12v, so it loads the 5v. But that also takes some power (albeit little) from the 12v line. To help prevent false peaks, adding a couple 4700uF 16v caps may help. The output of these supplies are fairly quiet from switching noise, but PC motherboards have caps all over the place in key areas to help. A cheapie PS might not be as tight.

@mvalentine6: I guess I missed your question. Even though it was posted a while ago: The 5v line is generally rated for a much higher current (usually at least 20A), so unless you plan to run the 5v line to the max, adding loading won't help.

MTBikerTim 09.23.2007 10:39 PM

No the false peaks on the charger were caused by my bought 12v power supply. Expensive little thing and the output was all over the place. As soon as I discovered the psu trick (I should of thought of it before) I sold the piece of **** off. Computer PSU have to provide very constant voltage. They are far better then most of the 12v converters that you can buy.

What's_nitro? 09.23.2007 11:15 PM

Just curious, what was your "piece of ****" PSU? I had a Radio Shack 10A PSU that gave me a false peak every once in a while back when I ran NiMH.

MTBikerTim 09.23.2007 11:42 PM

It was a ... I can't even remember. It wasn't really for charging batteries. It was for powering car fridges and had a fairly high amp rating. Higher them most computer psu anyway.

What's_nitro? 09.23.2007 11:47 PM

Ehh it probably wasn't regulated. Just a transformer, a rectifier, and some capacitors in an expensive black plastic box. :lol: Maybe not even the capacitors. :no:

BrianG 09.23.2007 11:50 PM

Unfortunately, with switching supplies, you generally get what you pay for. In the field I use a 17A PS and tweaked it for a little higher voltage (~12.5) to help the chargers switching circuit to operate a little better and to allow for more voltage dips under heavy load without going too low. At home, I use a nice Aston 35A supply tweaked to 14.5v, but it was something like $80-90 on eBay.

BrianG 09.23.2007 11:52 PM

Quote:

Originally Posted by What's_nitro? (Post 119569)
Ehh it probably wasn't regulated. Just a transformer, a rectifier, and some capacitors in an expensive black plastic box. :lol: Maybe not even the capacitors. :no:

Probably a linear regulator at that. You can usually tell by large TO-3 transistor(s) on the back on a largish heatsink. Switchers are MUCH more efficient.

What's_nitro? 09.23.2007 11:55 PM

I have a CAE 45A right now. Nice compact unit, built for powering high-end audio systems so you KNOW it's going to be stable.

BrianG 09.24.2007 12:02 AM

Too low power for that. :smile: Assuming you're running class AB amps (not class D), it would only be good for "only" ~450w rms max.

What's_nitro? 09.24.2007 12:26 AM

I use it to charge my batteries! Although it wouldn't be bad for a 10" sub on a class D mono with a good capacitor. I have two DTX ICE chargers to run at the same time, plus I use it to test ESCs. They really should put a switch on it for $200 though...

BrianG 09.24.2007 12:32 AM

I never liked the sound of class D. There's just something about them that sounds different, but I can't put my finger on it. So, I run only class AB and deal with the efficiency losses. I run an OLD PPI PC2600 on my sub and another OLD PPI PC2400 on a set of Diamond Audio 6.5" Hex drivers - also old. Sweet.

I would think running ESCs on a PS would be bad because of the reverse spikes from the motor. Maybe some transorbs would be better for that.

What's_nitro? 09.24.2007 12:42 AM

I don't test brushless systems for long, just to make sure everything's hooked up ok before I install it. Also makes it easier to program the ESC I think. I don't need to fiddle with batteries, just plug it in.

One of the downsides of listening to metal: subwoofers sound really crappy unless they're perfectly tuned. I had a pair of Logic Soundlab ZDX 12's with one of their LSX-2802 amps. The sound was crystal clear, and loud, except the music was like continuous thunder! Too much double-bass drumming I guess... Also if you go to their site, my ZDX subs had the same back structure as the EXL subs, and they could handle 2000W max! IDK why the changed them...

MTBikerTim 09.24.2007 03:37 AM

Yes what ever the stupid thing was it was crap. I never really tried to work out what sort of transformer it was. Live and learn I suppose. I now use a charger with the built in transformer and it's better but not that much. Still better then carting around a charger and big transformer though.


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