Jump to content



Sign up for a free account to remove the pop-up ads

Signing up for an account is fast and free. As a member you can join in the conversation, enter contests and remove the pop-up ads that guests get. Click here to create your free account.

Photo

anyone here that knows anything about DC-DC converting?


This topic has been archived. This means that you cannot reply to this topic.
21 replies to this topic

#1 of 22 OFFLINE   Dave_vega

Dave_vega

    Stunt Coordinator



  • 168 posts
  • Join Date: Dec 16 2002

Posted June 14 2004 - 05:10 PM

I want to run a Cyberhome 300 DVD player in my car..I have a 7" setup with an xbox with inverter I can take in and out of the car..I want to run this DVD player in the glove compartment..thing is the DVD player runs 10v DC at 2 amps..it has a power supply so it can be used in house on 110v..what I want to do is open the DVD player up and bypass the power supply and feed it a stable 10 volts..anyone know what would be the best way to do this? i'm guessing 9V DC is sufficient for this DVD player, because Cyberhome has a portable DVD player that runs 10v also and they have a converter that is 9v to run it..I was checking out car CD player universal converters and I found one that will do 9v at 2 amps..would this be the easiest way? or does anyone know anyone that can make a module to do this? thanks in advance..

#2 of 22 OFFLINE   Brad_Harper

Brad_Harper

    Stunt Coordinator



  • 132 posts
  • Join Date: Jul 05 2001

Posted June 15 2004 - 04:28 AM

I am going to assume this DVD player has an external power supply (like older laptop computers) that turns 110V AC into 10V DC.
In order to feed the DVD player 10V from the car battery follow these intsructions:

1. create a circuit board with 5 large diodes (10 amp +) wired in series. This will create a 3.5V drop which on a typical car will mean that approx 10V will be seen after the diodes. This is not a regulated supply so the voltage will fluctuate with battery charge.

2. Run a wire from the battery to a 2 amp fuse, and then from the fuse to the circuit board made in step 1.

3. Hook the circuit board to the power input of the DVD player.

4. Enjoy a movie!

Five diodes is just an estimate. You may only need 4 or you may need 6 to get the right voltage drop. It all depends on how good your vehicles charging system is. Diodes create approx 0.7 V drop across them. Providing a small over or undervoltage will not harm the internal electronics. Most gear is made to handle +/- 2V differences from spec. Just be sure to use large diodes so heat isn't an issue. Small ones will burn up at larger currents.

#3 of 22 OFFLINE   Dave_vega

Dave_vega

    Stunt Coordinator



  • 168 posts
  • Join Date: Dec 16 2002

Posted June 15 2004 - 01:26 PM

thanks for the help brad..do you possibly have any links to the diods and circuit board?

#4 of 22 OFFLINE   Brad_Harper

Brad_Harper

    Stunt Coordinator



  • 132 posts
  • Join Date: Jul 05 2001

Posted June 16 2004 - 12:09 AM

The circuit board you will probably have to make yourself unfortunately. The diodes you can pick up at any electronic parts store. Rectifier diodes will work best. You probably really dont need a board, you just have to solder the diodes together in series. Most diodes have flexible leads so you should be able to make something compact easy enough.

#5 of 22 OFFLINE   Brad_Harper

Brad_Harper

    Stunt Coordinator



  • 132 posts
  • Join Date: Jul 05 2001

Posted June 15 2004 - 04:28 AM

I am going to assume this DVD player has an external power supply (like older laptop computers) that turns 110V AC into 10V DC.
In order to feed the DVD player 10V from the car battery follow these intsructions:

1. create a circuit board with 5 large diodes (10 amp +) wired in series. This will create a 3.5V drop which on a typical car will mean that approx 10V will be seen after the diodes. This is not a regulated supply so the voltage will fluctuate with battery charge.

2. Run a wire from the battery to a 2 amp fuse, and then from the fuse to the circuit board made in step 1.

3. Hook the circuit board to the power input of the DVD player.

4. Enjoy a movie!

Five diodes is just an estimate. You may only need 4 or you may need 6 to get the right voltage drop. It all depends on how good your vehicles charging system is. Diodes create approx 0.7 V drop across them. Providing a small over or undervoltage will not harm the internal electronics. Most gear is made to handle +/- 2V differences from spec. Just be sure to use large diodes so heat isn't an issue. Small ones will burn up at larger currents.

#6 of 22 OFFLINE   Dave_vega

Dave_vega

    Stunt Coordinator



  • 168 posts
  • Join Date: Dec 16 2002

Posted June 15 2004 - 01:26 PM

thanks for the help brad..do you possibly have any links to the diods and circuit board?

#7 of 22 OFFLINE   Brad_Harper

Brad_Harper

    Stunt Coordinator



  • 132 posts
  • Join Date: Jul 05 2001

Posted June 16 2004 - 12:09 AM

The circuit board you will probably have to make yourself unfortunately. The diodes you can pick up at any electronic parts store. Rectifier diodes will work best. You probably really dont need a board, you just have to solder the diodes together in series. Most diodes have flexible leads so you should be able to make something compact easy enough.

#8 of 22 OFFLINE   Dave_vega

Dave_vega

    Stunt Coordinator



  • 168 posts
  • Join Date: Dec 16 2002

Posted June 20 2004 - 03:39 PM

thanks again brad..I was talking a guy I know about these diodes and he suggested a large 20 watt resistor..he said it would do the same thing..any clue about the resistors? he said I would need a 1.2 ohm resistor to make the drop from 12v-10v..i'm just trying to figure out what would be easier..and 1 big resistor would suit my needs better I think..thanks in advance..

#9 of 22 OFFLINE   Dave Milne

Dave Milne

    Supporting Actor



  • 569 posts
  • Join Date: Jul 02 2001

Posted June 21 2004 - 01:23 AM

Dave,
The diodes are really better than the resistor. They provide relatively constant voltage drop regardless of current. The resistor is going to result in large voltage fluctuations as current changes (DVD playing, not playing, drawer motor energized, etc). Even the high-frequency current fluctuations caused by the digital circuitry will cause lots of power line noise with a resistor installed.

If you're looking for a one-part solution, a fixed 10Vdc voltage regulator like LM7810 would be great. Problem is, the 7810 has fairly high drop-out (2.0 - 2.5V). So, if the car is off and the battery dips below 12, it will fall out of regulation. Somebody probably makes an LDO (low drop out) fixed 10V regulator. I'll take a look and see what I come up with. You can always use an adjustable LDO regulator, but that requires a few more parts.

#10 of 22 OFFLINE   Dave_vega

Dave_vega

    Stunt Coordinator



  • 168 posts
  • Join Date: Dec 16 2002

Posted June 20 2004 - 03:39 PM

thanks again brad..I was talking a guy I know about these diodes and he suggested a large 20 watt resistor..he said it would do the same thing..any clue about the resistors? he said I would need a 1.2 ohm resistor to make the drop from 12v-10v..i'm just trying to figure out what would be easier..and 1 big resistor would suit my needs better I think..thanks in advance..

#11 of 22 OFFLINE   Dave Milne

Dave Milne

    Supporting Actor



  • 569 posts
  • Join Date: Jul 02 2001

Posted June 21 2004 - 01:23 AM

Dave,
The diodes are really better than the resistor. They provide relatively constant voltage drop regardless of current. The resistor is going to result in large voltage fluctuations as current changes (DVD playing, not playing, drawer motor energized, etc). Even the high-frequency current fluctuations caused by the digital circuitry will cause lots of power line noise with a resistor installed.

If you're looking for a one-part solution, a fixed 10Vdc voltage regulator like LM7810 would be great. Problem is, the 7810 has fairly high drop-out (2.0 - 2.5V). So, if the car is off and the battery dips below 12, it will fall out of regulation. Somebody probably makes an LDO (low drop out) fixed 10V regulator. I'll take a look and see what I come up with. You can always use an adjustable LDO regulator, but that requires a few more parts.

#12 of 22 OFFLINE   Dave_vega

Dave_vega

    Stunt Coordinator



  • 168 posts
  • Join Date: Dec 16 2002

Posted June 21 2004 - 08:52 AM

thanks alot dave..I jut wanted to make sure that the diodes were the best option..I appreciate all your help..

#13 of 22 OFFLINE   Dave_vega

Dave_vega

    Stunt Coordinator



  • 168 posts
  • Join Date: Dec 16 2002

Posted June 22 2004 - 01:47 PM

ok I made the resitor today..I put 7 3 amp diodes in series..the 6 amp diodes were like 5 bucks a piece so the 3 amp will have to do..I doubt the DVD player will come even close to 2 amp so it should be good..as far as the readings this is what I came up with for 7 diodes..

car off at the battery it was 12.37v
car on at the battery was 14.5v
after the circuit with car off it was 9.6v
after the circuit with the car on it was 11.51v

I only got a 3 volt drop with 7 diodes..kind of weird when they are supposed to be 0.7v drop for each..

now I know there is a tolerance of 1-2v either way, but i'm thinking I should use another diode to lower the voltages to 9v (car off) and 10.8 (car on)..

any thoughts?

#14 of 22 OFFLINE   Dave Milne

Dave Milne

    Supporting Actor



  • 569 posts
  • Join Date: Jul 02 2001

Posted June 23 2004 - 12:31 AM

Dave,
When you took your measurements, was the DVD player connected and playing? The forward drop on the diodes will increase a little as you pull current through them. That's why a regulator would have been a better (but possibly more complex) option.

Anyway, I would stick with what you have. The DVD player undoubtedly has internally regulated power supplies... so a little overvoltage is not going to hurt. Too low, and you may trigger a power-on-reset function and it will shut down.

#15 of 22 OFFLINE   Dave_vega

Dave_vega

    Stunt Coordinator



  • 168 posts
  • Join Date: Dec 16 2002

Posted June 21 2004 - 08:52 AM

thanks alot dave..I jut wanted to make sure that the diodes were the best option..I appreciate all your help..

#16 of 22 OFFLINE   Dave_vega

Dave_vega

    Stunt Coordinator



  • 168 posts
  • Join Date: Dec 16 2002

Posted June 22 2004 - 01:47 PM

ok I made the resitor today..I put 7 3 amp diodes in series..the 6 amp diodes were like 5 bucks a piece so the 3 amp will have to do..I doubt the DVD player will come even close to 2 amp so it should be good..as far as the readings this is what I came up with for 7 diodes..

car off at the battery it was 12.37v
car on at the battery was 14.5v
after the circuit with car off it was 9.6v
after the circuit with the car on it was 11.51v

I only got a 3 volt drop with 7 diodes..kind of weird when they are supposed to be 0.7v drop for each..

now I know there is a tolerance of 1-2v either way, but i'm thinking I should use another diode to lower the voltages to 9v (car off) and 10.8 (car on)..

any thoughts?

#17 of 22 OFFLINE   Dave Milne

Dave Milne

    Supporting Actor



  • 569 posts
  • Join Date: Jul 02 2001

Posted June 23 2004 - 12:31 AM

Dave,
When you took your measurements, was the DVD player connected and playing? The forward drop on the diodes will increase a little as you pull current through them. That's why a regulator would have been a better (but possibly more complex) option.

Anyway, I would stick with what you have. The DVD player undoubtedly has internally regulated power supplies... so a little overvoltage is not going to hurt. Too low, and you may trigger a power-on-reset function and it will shut down.

#18 of 22 OFFLINE   Dave_vega

Dave_vega

    Stunt Coordinator



  • 168 posts
  • Join Date: Dec 16 2002

Posted June 23 2004 - 01:37 PM

hey dave..i got the DVD player today and ripped it apart..the AC power went into a circuit board and then out to the actual DVD tray..there were 2 voltages..12v and 5v and 2 grounds..i'm guessing the 5v is for the actual board much like a mobo I guess..anyway I made the circuit to compensate for this..I just added diodes and took the 5v power further up the circuit..

for the 12v I now have readings of 11.5v with the car off and 13v with the car on..the highest reading I got on the DVD player when it was stock was 12.12v on the 12v wire..i'm guessing 11.5 and 13v will be fine..on the 5v wire I have a reading of 4.8 with the car off and 5.7 with the car on..this is actually right around where the voltage was on the 5v wire..tomorrow I have to complete the project..I just have to wire the power and ground in the car and then attach it to the modded DVD pplayer..i'll be sure to take pictures in case this actually works Posted Image thanks again for the help..

#19 of 22 OFFLINE   Dave_vega

Dave_vega

    Stunt Coordinator



  • 168 posts
  • Join Date: Dec 16 2002

Posted June 23 2004 - 01:37 PM

hey dave..i got the DVD player today and ripped it apart..the AC power went into a circuit board and then out to the actual DVD tray..there were 2 voltages..12v and 5v and 2 grounds..i'm guessing the 5v is for the actual board much like a mobo I guess..anyway I made the circuit to compensate for this..I just added diodes and took the 5v power further up the circuit..

for the 12v I now have readings of 11.5v with the car off and 13v with the car on..the highest reading I got on the DVD player when it was stock was 12.12v on the 12v wire..i'm guessing 11.5 and 13v will be fine..on the 5v wire I have a reading of 4.8 with the car off and 5.7 with the car on..this is actually right around where the voltage was on the 5v wire..tomorrow I have to complete the project..I just have to wire the power and ground in the car and then attach it to the modded DVD pplayer..i'll be sure to take pictures in case this actually works Posted Image thanks again for the help..

#20 of 22 OFFLINE   Dave Milne

Dave Milne

    Supporting Actor



  • 569 posts
  • Join Date: Jul 02 2001

Posted June 25 2004 - 01:17 AM

Woah! Now I'm confused. I, like Brad, assumed that this thing was powered with some sort of "wall wart" that output 10 Vdc

Quote:
I am going to assume this DVD player has an external power supply (like older laptop computers) that turns 110V AC into 10V DC.

I dind't realize you were going to go inside the unit. According to their website, there is a

Power Switching Adapter:
• Input: AC 100~240V 50/60Hz 0.41A
• Output: DC 10V, 2A

Where is this "switching adapter"? Inside the unit? The picture shows a standard 110V connection on the pack panel.

Quote:
for the 12v I now have readings of 11.5v with the car off and 13v with the car on..the highest reading I got on the DVD player when it was stock was 12.12v on the 12v wire..i'm guessing 11.5 and 13v will be fine..on the 5v wire I have a reading of 4.8 with the car off and 5.7 with the car on
This is fine for 12V. I'm concerned, though about the 5. Digital devices, especially microprocessors, are very picky about their 5V supply. 5.5 is usually the spec max.





Forum Nav Content I Follow