How do I change 13.8v dc to 6.5-7v dc

[xpuser8334]

Could anybody please help.

I need to change Car Voltage 12.0 - 13.8v DC to 6.5 to 7 Volts.
I Believe i can use resistors, but don't know which ones.

I an trying to power up an old sony handycam using the Cigarette Lighter on a boat (For Wake-Boarding / Skiing Instruction)

Thanks In Advance

 

[magnet]

u can buy a cigarette lighter converter from most camera shops, i think thats ur best option m8. about £10 would b a fare price to pay.

 

[Spectre]

Yes m8, the best idea would be to buy a proper regulator maybe Maplin do one ? Using resistors for voltage dropping like that isn't the best solution

 

[mitch]

try this m8

you could use two 10k resistors
solder them together in a line add a feed from pos from your batt+ at one end and a feed from - at the other to get your 6-7 volts out put the + to your cam in between the two resistors and the - at the same end as the - from bat.

this should work the voltage between the two resistors should be half of the input voltage ie 13/2=6.5

 

[pete252]

Maplins do a power adaptor, with numerous power connectors, stock code JY53 for a tenner but check the current requirements for your cam. The adaptor will only supply 500mA....

www.maplin.co.uk

Pete

 

[Taff]

I do not think the two 10 k resistor theory is gonna work..

I agree in principle that as long as the two resistors wired in series are of equal size then you are gonna get en equal potential difference (volate drop) across them thus halving the voltage but remember the camera has an internal resistance (little 'r') if you know the rating or current of the camera then this little 'r' can be calculated using ohms law .....
this does not take into account fluctuations in the volatge from the boats supply hence the need for a regulator..

why not just charge the handycams battery up before usage....

 

[xpuser8334]

Thanks For That Guys.

Thanks Guys,

The Camera was given to me, and eats batteries,
while being towed at the back of a boat at about 20mph, changing the batteries is NOT a good Idea,

I will try my local camera shop again for any adapters they keep saying are NOT available. (but never look in any of their catalgues!!!)

I have changed voltages before using a "Potential Divider" I think it was called, but this was at school almost 14 years ago, and I cannot remember much that far back, God help me when I get to 40.

Thanks Again.


Wayne.

 

[cyggy]

Change 13.8vdc to 7vdc

I posted a reply nearly 3 weeks ago but it hasn't shown. I still say one of the easiest ways to lower a dc voltage is to run a set of diodes in series. Each diode drops 0.6v so to drop 6.6volts use 11 small diodes in series (or 12 for a little more safety). Mount them on a small piece of veroboard ( all pointing in the same direction). Regardless of the current taken, within the capacity of the diodes, the voltage will be constant. Diodes of 1amp are very cheap and the whole thing need cost no more than £1 to £2 pounds. The thing can be mounted in an old tobacco tin or plastic box. There is no heat loss to worry about and it is far safer than resistors. I am not a computer expert but I was a Senior Lecturer in electronics and have used this idea many times. Cyggy.

 

[Taff]

If there is a voltage drop of .6 of a volt then the first law of thermodynamics states that the total amount of energy remains unchanged in any transformation process ( If the energy at the output is less than the input then the energy must have been converted to another process (usually wate heat)..

A diode is a semiconductor device so passing a current through it should generate heat also , I have seen and burned my hand on hot diodes on more than one occasion....so I must disagree on the heat loss theory...

im afraid with the dc supply the only option is using a suitable load to provide a suitable voltage drop...

zener or reference diodes are good at regulatingthe volatge after the drop....

Another idea I have just had

instead of 1 12 volt battery use 2 6 volt batteris in series and run the camera from between one of the batteries thus there is your 6 volts ....

EASY..........................

 

[cyggy]

changing dc voltages

Taff, if a diode is running hot enough to burn your fingers, it is being overloaded or it needs to be metalcased with heatsink! We are talking small currents here, so by all means use a resistor and zener, but it is so simple to use series diodes (as long as you don't exceed their rated current and we needn't worry about their peak-inverse-voltage in this particular case). Try it and I promise you will be happy!!! I just wish I knew how to use this computer to draw circuits, I would sketch it all out for you. If the young man in question wants more details, I will be happy to help. If only I felt as confident with computers...........but I only started a few months ago and old age has taken up some of the volatile memory although my hard drive still works!! Cyggy

 

[Taff]

dont forget with old age comes experience and knowledge...


as for being new to computers we all had to start somewhere, im sure youl be an expert in no time.....

 

[Spectre]

A busy topic indeed :

Yes cyggy I agree (I am a lowly test Engineer : ) A few 1N4007s would do the trick, even 1N5002 if you wanted it a bit more current.

Pos + --->I--->I--->I--- To camera

Sorry about the ASCII drawing but the idea is there, maybe 10 diodes or so to get it right

 

[Taff]

Yes I agree the diodes will provide the required voltage drop, I was just concerned about heat dissapated.. although I have never used diodes for volatge drop it is a handy thing to know..

I can only remember the 1N 4000 series diodes and now they have a 5000 series cool...

I have only really required the use of diodes for rectification and yes I agree with you cyggy as the diodes were hot there must have been a prob (maybe wrong didode selection).......

I must again mention my revelation as it came to me last night and I still think it is the perfect solution... the two 6 volt batteries connected in series.. they would provide the required 12 volt output but connection for the camera accross only one battery would provide the 6v odd supply for the camera...

come on ... this might be my crowning moment where simplicity defeats technology.....

:Clap: lol worth a try... I hope XPUSER managed to solve his prob anyway..

spectre .. "TEST ENGINEER" what a cool sounding job...

 

[cyggy]

VD (er, Voltage Drop)

Should be PD of course but good for a laugh. Well, Spectre and Taff, I felt like a fish out of water on this site with you blokes all banging out your messages on computing, but I've got my toe in there now and I won't let go. I used to lecture in Radio/TV/Video/HIFI/Radio Amateur and some Industrial Electronics so I might be of some use occasionally, though the good days have gone in much of it. Spent a lot of time in industry also in Electrical/Electronics design so a long life with a permanent soldering iron stuck in the fist! Loved every minute of it and Spectre, there ain't no such thing as a LOWLY electronics man. They are the salt of the earth mate. Cyggy

 

[Spectre]

Such a nice thing to say m8s Doh, these sort of things cause probs in stores at work...It is a 1N5_4_01/2 etc... it was a late post and I was getting slow (Remove underscores ). But I do hope to be in a full design capacity one day, test rigs are fun but some day....rool:

 

[Spectre]

Oh, and yeah please stick around Cyggy I'm sure there will always be something to tickle your fancy here...If there isn't just suggest something...It could lead somewhere quicker with more minds on it

 

[cyggy]

DC Control

Taff and Spectre, I think we might have scared the life out of xpuser, he hasn't replied since we started arguing the toss! Don't be scared mate, come on in the water's fine! Cyggy

 

[Spectre]

Ooop....Yes xpuser if you are still here we would like to see you get your adapter as well.

 

[vfr]

step down regulator

Hi Guys
This is a problem encountered by a lot of people, The best solution that I have found is a National Semiconductor part LM2576T. This is a switch mode regulator chip that is used in regulated power supplys delivering high currents.
This regulator will drop the voltage to what you require and in the case of a cam corder several amps may be required.
This little device will drop 13 volts to 6Volts and deliver currents of up to 3 amps with the small heatsink on the device just getting warm. The part is available from Maplin. Application notes are available from the National Semiconductor web site
vfr