6v to 12v conversion

[rpaull]

I manufacture and sell a product that runs 12v 1amp LED’s. I currently use 8 C cell batteries to achieve the 12 volts. I would like to reduce this to 4 batteries. Is there an easy way to convert the 6v from 4 batteries into 12v at 1 amp?

I already encase a switch and 12v plug into a small potting box and am hoping I can find a way to encase the 6v to 12v parts as well.

Raymond

 

[markus.dnd]

sounds like step up converter.

make sure that batteries can supply enough watts for circuit losses and leds berfore you start building it.

Markus

 

[(*steve*)]

I would consider changing the arrangement of the LEDs so that they can be powered from 6V rather than 12.

Alternatively, google DC-DC converter and see what you can find.

 

[NickS]

We had a pretty good discussion on converters here
https://www.electronicspoint.com/cell-phone-and-pod-charger-lithium-battery-t222071.html

 

[rpaull]

Thank you for the help

I tried the National Semiconductor site and found it helpful. I think there is definitely a DC-DC Boost Converter out there that will work now I just need to find it. I don't know enough about electronics to make the design area usable but I think they will be able to help me out if I drop them an e-mail.

The previous thread also helped me understand the terminology better.

I also googled DC-DC boost converter and found Digikey has a tun. Once again I need to figure out which one will work. Hopefully they can help if I e-mail or call them.

The LEDs I am using are 12vdc, 20Ma and .24w. There are 72 of them. Am I correct that the boost converter will need to produce at least 17.28W?

Raymond

 

[NickS]

Tell us more about the configuration you are using. It sounds like you are powering all 72 LED's in parallel? And your calculation of 12V @20mA do you really need 12V for each LED? Is it possible to either combine LED's in series or reduce your Vdrop(and series resistors)?

Perhaps you have it all figured out but I am unclear about it after looking at your power calcs.

 

[rpaull]

LED configuration

The LED's are supplied in modules that are all connected in a row by a positive and negative wire running from each module to the next. There are 3 LED's on each module. They come with a 12v 1000ma power supply. I also run them off 12v from 8 batteries in series. I am not sure how the LED's are wired together in each module. I know if you wire them backwards they don't work. They last for several days on 8 C batteries then slowly start to get dimmer over the next several days. I would think they are in parallel so that if one goes out the rest don't also quit working.

 

[vk5ajl]

I know the modules you are talking about. There are 3 leds (the ones I know are white) in each module in series with a single surface mount resistor also in series to limit current. The voltage drop across white leds is about 2 and a bit meaning more than 6v across the leds. Unless you want to change the surface mount resistor you are stuck with 12v. Since the 3 are all in series and if they take 20mA, it means .24w for each module.

Have you got 72 leds or 72 modules. If 72 leds the power you need to convert is a bit under 6w. (.24w per module x 24 modules). This is easy with a small 50% duty cycle flyback converter.

 

[rpaull]

great

There are 24 modules and 72 leds. That is great that a simple part might fix my problems. I am also looking into just using 6v leds but need to find a new supplier. My supplier in china doesn't carry them. Maybe there is one that has 6v leds that are just as bright for the same price.

I will definitely try an find this 50 50 converter to use until then.

 

[rpaull]

vk5ajl,
I found a couple on google:
http://cgi.ebay.com/ws/eBayISAPI.dl...ffec675&itemid=170148466627&ff4=263602_263622
and
http://cgi.ebay.com/ws/eBayISAPI.dl...ffec675&itemid=350177045025&ff4=263602_263622

Both of them look like a computer chip with 8 terminals. I assume they come with some sort of electrical schematic but with a part that small and specific I could be rong. Do you think i can wire it with just the + and - in from the battery and end up with a + and - out for the LEDs? I am guessing that some of the terminals get wired together or are just left alone.

Would you suggest I also get a part to receive the chip or can I just wire it and put it in the potting box with the other stuff?

 

[vk5ajl]

Both of those circuits require 8v and are Pulse Width Modulators and I don't think suitable to convert 6v. They require external components as well. Type the numbers into Google with the word DATASHEETto see how they are used. There is a capacitive pump circuit I used in anciet history for converting +5v to ±12v for RS-232 use but don't ask me to remember what it was. Any IC designed for converting up will require external components. I have done it with a 555 timer (and associated timing components), a couple of transistors, a couple of diodes and capacitors. In SMD the whole thing came to about 15mm x 15mm and powered a few watts but it would need bigger bits for 6w.