I've modified an ipod dock to work in my car, however when it's powered off the cars DC power I get an annoying interference on OE navi screen in my 07 TSX. I thought it might be from the engine, but when the engine's off, it's still present. If I bring an extension cord out and use the AC/DC home transformer there's no interference at all, but when I power it up from the car's DC it's back. Can I filter this out somehow? Also, not sure how important this is, but the home's AC/DC transformer "block" output spec is 10VDC 1.5A, I couldn't find a DC/DC transformer with that exact spec, so i'm using a 9VDC transformer. Could the -1 volt make a difference? Help, I'm going crazy here!

a description of the interference: translucent white bars traveling up the screen in a uniform pattern and every once and a while they gradually speed up and seem to "sync" then change direction and slow down.

Sorry if this has been covered, but Mike screwed up the search feature and doesn't know how to fix it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Honduh Chicken &raquo;</TD></TR><TR><TD CLASS="quote">Could the -1 volt make a difference? Help, I'm going crazy here!
</TD></TR></TABLE>

Absolutely. Power it properly and I bet the interference goes away.

 

sweeeet. thanks!

Do you know the best way to provide my source with the power it needs? I have to get 12VDC -&gt; 10VDC. I've been told this can be done simply by putting the proper resistors inline with the (+). Any truth to this? If so, how do I find the formula to calculate how much resistance I will need? (aside from just buying a box of resistors and testing)

 

Yes, use resistors.

http://en.wikipedia.org/wiki/Ohm's_law

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by suspendedHatch &raquo;</TD></TR><TR><TD CLASS="quote">Yes, use resistors.

http://en.wikipedia.org/wiki/Ohm's_law</TD></TR></TABLE>

I used resistors, found the exact resistance needed to obtain 10.25 volts, spent a bunch of time soldering them together, heat shrinking them together and making them look nice, just to find that when a load is applied, the current made the voltage drop to almost nothing.

What a waste of ******* time, I just decided to buy a $25 power inverter from Radioshack and used the supplied home transformer. I kick myself in the *** for not doing this sooner because it works like a charm! Forget resistors or home built DC/DC step downs, I'ma get a 12V accessory socket, plug this thing in, tape it together, and wire tie it up behind the radio.. g'night.

 

It can be done, lol paintence is the key. Also what hte hell is your avatar doing

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wrx-killer-Sti-eater &raquo;</TD></TR><TR><TD CLASS="quote">It can be done, lol paintence is the key. Also what hte hell is your avatar doing </TD></TR></TABLE>

lol it's flat eric. and he's rockin out to a little Mr. Oizo.

http://en.wikipedia.org/wiki/Flat_Eric


Modified by Honduh Chicken at 10:03 AM 8/7/2007

 

Flat beat rules!!

http://www.youtube.com/watch?v=YQXiew-DQH4

 

What size resistors did you use?

 

1 MOHM

I actually used (3) 1Mohm resistors in parallel.

 

You'd need a 2 ohm resistor to drop ~3v at 1.5 amps. 300k ohm is way too much resistance.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 02 accord &raquo;</TD></TR><TR><TD CLASS="quote">You'd need a 2 ohm resistor to drop ~3v at 1.5 amps. 300k ohm is way too much resistance.</TD></TR></TABLE>

The problem I run into is, with 2 ohm and no load (ie, you power the unit down) the voltage spikes to 13.8VDC which is too much for the internal circuitry of the unit. The engineer at the mfg told me +-5%.

 

The proper way to do this would be to get a an adjustable voltage regulator and set it for ~10v. That voltage would stay constant no matter what the load is.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Honduh Chicken &raquo;</TD></TR><TR><TD CLASS="quote">I couldn't find a DC/DC transformer with that exact spec, so i'm using a 9VDC transformer. </TD></TR></TABLE>
DC transformers dont exsist what are you using? I'm guessing it's some kind of switching power supply which would explain the noise.

Resistors are a bad idea the voltage will change as the load changes. You want a voltage regulator.

http://www.radioshack.com/prod...earch

OR

http://www.digikey.com/scripts...-5-ND


Modified by nsxxtreme at 9:44 AM 8/7/2007

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxxtreme &raquo;</TD></TR><TR><TD CLASS="quote">
DC transformers dont exsist what are you using? I'm guessing it's some kind of switching power supply which would explain the noise.

Resistors are a bad idea the voltage will change as the load changes. You want a voltage regulator.

http://www.radioshack.com/prod...earch

OR

http://www.digikey.com/scripts...-5-ND


Modified by nsxxtreme at 9:44 AM 8/7/2007</TD></TR></TABLE>

I SAW that! I was reading the back of the package, and it appears that you can set the output voltage by adding resistance to one of the pins and running it inline with the ground, they offered a formula, but I couldn't understand the formula or the schematic. I'm not an electrical engineer, but I can solder a circuit board if I have someone help translate the schematic.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Honduh Chicken &raquo;</TD></TR><TR><TD CLASS="quote">I SAW that! I was reading the back of the package, and it appears that you can set the output voltage by adding resistance to one of the pins and running it inline with the ground, they offered a formula, but I couldn't understand the formula or the schematic. I'm not an electrical engineer, but I can solder a circuit board if I have someone help translate the schematic. </TD></TR></TABLE>
If your really interested I can help you out.

The one from digikey is a fixed volatge version. Meaning there are no resistors to configure.

 

If you use the voltage regulator you are going to also want to buy a heatsink to disapate the wasted energy.

(14.4-10)= 4.4V drop *1.5amps=6.6watts

A normal heatsink from radioshack should work. I would also put a 10V zenor diode in parallel with the output that way if the regulator failed you would not exceed 10V.

Put a 2amp fuse inline with the regulator and a regulator failure would cause the zenor diode to activate and blow the fuse.