Help with 12V to 5V setup, having powering issues.

**Mickz** · 10-18-2011, 02:11 AM

Just a couple of thoughts, The TR7 has pulsed outputs but I haven’t seen that indicated for the TR4.

I would switch +12v input to 12v to 5v unit instead of +5 output. Less current demand on the relay but if you only drawing low current then I guess it doesn’t matter.

I carried out some tests with powering +5v to the HUBs before the PC had powered up. Got strange results with various USB devices not initialising at start-up. The MS web cam shows up as an unknown device on the bus. Results were consistent every time and this was with a Linear +5v regulator.

I have one of those inverters you use here, mine is a 100 watt unit. Had quick test and it appears to start up fine with no delay, however as the spec said, 12v- 24v input but will run 10v to 24v. There is a definite on/off pulse and low voltage with anything below around 10.1 volts. I would imagine that if over 10v was not immediately available at start-up then it may give some strange results. It’s also not a clean cut-out of +5v output if the input voltage dips to around 10v.

Have you tried something simple like a large cap across the output of the inverter? I think your unit is rated at 20A so there should not be a problem with inrush current with a largish cap.

Just some random thoughts, on the way out so I may have misunderstood something with my quick read of your problem, apology if so.

**OldSpark** · 10-18-2011, 03:34 AM

Gi'dam...
Things like....

Originally Posted by Mickz

Have you tried something simple like a large cap across the output of the inverter? I

scare me.
I think inverter... dc to ac... no cap across ac (well, not to filter below 50/60Hz etc).

Flashback - capacitors on PWM outputs...

Not that I recall a inverter in this thread. I thought it involved converters - ie, dc-dc.

Ah, jargon fun.
dc-dc converters involve inversion or inverters but are called converters, not inverters - at least in my general experience.
Inverters are dc-ac. But aircons and welders now have "inverters".
And UPS were thought of as ac-dc-ac but can include ac-dc (and dc-dc).

Yes, it pays to know the audience and THEIR jargon.

At least ships still carry CARgo and cars carry SHIPments.

As to relays NOT isolating batteries....

**Mickz** · 10-18-2011, 04:13 AM

Yes, that’s just me spewing something out quickly, like I said, in a hurry at the time.

It’s a 20A DC to DC Step down Convertor and a cap may help ease any weird voltage fluctuation that may be happening at start up or at least identify if there is a problem there.

This device is short circuit proof.

**Mickz** · 10-18-2011, 04:14 AM

Strange forum happenings here, double posts and no response most of the time. Tried to delete this second post that apeared.

**HiJackZX1** · 10-18-2011, 11:01 AM

Yea, they are trying to add a new feature to the forums and its causing chaos.

**HiJackZX1** · 10-18-2011, 01:57 PM

What are OldSpark and Mickz talking about? You guys lost me. Im going to head to Radioshack and see if I can find a capacitor and diode.

**HiJackZX1** · 10-18-2011, 04:19 PM

OK, I had a hunch.... I was using 2 different PSUs to power each item. Once I combined the connection to one, it all worked perfectly.

**OldSpark** · 10-18-2011, 06:45 PM

You have connected 2 supplies together (ie, their outputs)?

That is usually risky, but sufficient output resistance else appropriate design can save the day.

(Speaking of which I recently read threads where they increased the output voltage of one ATX rail by increasing the load on the other. IE - bad design - a shared ground path. I prefer to add diodes or change the feedback resistance!)
Now let's see if this double-posts....