Dew controler based LED dimmers

[Duke2k]

Thanks for the info. If I use the 7806 will I need anything else and how is it wired up? I see that some designs use heatsinks I presume these are needed?

Thanks

Arthur

[Duke2k]

Sorry The LM317 is an adjustable regulator? How would I wire this and what resistors would I need?

Thanks

[malc-c]

Dude, ever heard of yahoo or google ?

There are tons of circuits on the web with examples of how to wire the LM317, As for the 7806, it depends on what you are powering it from and how much current will be drawn from it. The obvious is a decent heatsink to keep it cool if it's drawing an amp or more (normally these are 1amp devices, but some are rated at 2amp). A couple of small 10uf capacitors often help smooth the supply. With the LM317, it is advisable to have a volt meter to hand to check the voltage as it's adjusted so you get the correct 7.4v under load

You've not stated what it is you will be running from the 6v and 7.4v lines... and it's clear you've never ventured into electronics. If you have expensive equipment that will be powered from this unit, then you need to be sure and confident that you are getting things right as you could end up blowing things up. I'm not trying to put you off, but would suggest you do your own research and only proceed if you are confident you won't damage the equipment your work will be powering

[Duke2k]

Well thanks for the help. I am just trying to save myself some money and seeing all of the help that has been given on this forum I presumed that this was the place to ask especially as you have already made one! Yes there are many circuits available on google but how would I know which one is right for this purpose? The 6v supply is to power an eq2 ra motor and the 7.4v is to power my Canon SLR. I thought that asking for help from people who know what they are doing was the best kind of research but obviously not.

[malc-c]

Asking questions is fine, but as I explain to my kids, it much better to come to me with some basic findings and then ask if it will work or which is best rather than expecting someone else to do it for you !

Anyway, which Canon dSLR are you trying to run.

Googling "cannon battery eliminator circuit" throws up several offerings

http://www.beevo.com/canon_battery.htm

this circuit provides an 8.4v output, but could be adjusted by changing values of R2 (using a trim pot you could set the required voltage to whatever your want) http://dronecolony.com/2008/09/26/diy-ac-adaptor-for-the-pentax-k10d/#comments most of the LM 317 / 318 regulator circuits will be the same, just with slightly different values for the capacitors and resistors depending on the output voltage and if it's fixed or varible

I used a standard 7886 2amp regulator to power my Canon D400 from a 13.8v supply - similar to this http://blog.stefanvds.com/2011/11/30/diy-canon-ac-adapter/

There you go... for starters.

[Duke2k]

Ok thanks I did electronics at school but that was 40 years ago. I know how to make a voltage divider to drop the voltage using resistors but the regulators were new to me. As for the LM 317 adjustable regulators that I looked at, none mentioned using a heatsink whereas the 7806 did.

Arthur

[Gina]

Depends on the current - if you want to use anywhere near the LM317T 1.5A current limit, you'll want a heat sink.

[malc-c]

The formula for working out what size heatsink to use is quite complex ( see http://www.datasheetcatalog.org/datasheet/SGSThomsonMicroelectronics/mXusyv.pdf ) - the simple way is to turn it on under load with a finger placed on the device and if it gets hot that you can't hold your finder on it, turn it off and fit a heatsink !!

[Cubemaster]

Duke2k,

I was in pretty much the same boat as you when I started out in electronics again but I Googled and Googled and Googled until I understood and these kind people also put me on the right path by following their work

This is basically the circuit I used for the 6v (though change the 7805 to a 7806). You can maybe also build another identical circuit with a 7808 (read somewhere you can put a 1N4004 diode in series for exactly 7.4v) but someone in here can correct me if I'm wrong as the 7808 may actually put out 8.6v?

Personally I'd go LM317 with the correct resistors for the required voltage.

Dave

[Duke2k]

Thanks everyone I have ordered the parts on daves diagram and will let youknow how things go.

Arthur

[malc-c]

Hi all, I have been following this post for a few weeks now while waiting for my dimmers to arrive. I have got four dimmers which will all be used for dew heaters, and I understand how to wire these up but I also need 2x 12v outputs 1x 6v output and 1x 7.4v output. I have a limited knowledge of electronics and wondered if anyone could tell me how to drop the 12v to 6v and 7.4volts? I also noticed a post about adding a resistor to the pot to give maximum output at the maximum setting but I dont really understand this.

OK hopefully the attached diagram and schematic (found the schematic for the LM314 circuit using google the other was a sketch from my previous post) will help.

12v in, 4 dimmers, 2 x 12v out, 1 x 6v out (using a 7806), 1 x 8.6v (using 7886), and a 7.2v out (using a LM314).

This assumes you are using a 13.8v regulated power supply or a well charged 12v powerpack. If you are using a cheap 12v supply then make sure you add some smoothing capacitors across the input and outputs of the linear regulators. Heatsinks are advisable

Forgot to add, that you could play with the resistors on the adj pin to up the voltage to 7.4v

[Cubemaster]

Wow Malcolm!

That really is helpful for anyone else following

Dave

[malc-c]

I try

Just wish to add that its just a suggestion. Anyone using it would need to check the pin outs of the regulators used as some manufactures seem to swap the in and out pins, and that I've never used the 7.2v circuit, just that it was one of the most descriptive I found on google.

[Duke2k]

Thanks Malc thats exactly what I need.

Arthur

[Duke2k]

I will be powering the controller from a 13.8v regulated supply while at home and a 17ah battery pack while away. 2 or 3 dew heaters will be used at one time along with 1 of the 12v outputs. When using the mount to guide my camera then it will be 1 heater the mount and the camera, so I will never use all of the outputs at the same time but the option to use it for different applications seemed a good idea.

Anyway thanks to you all for your help!

[allcart]

I need some advice on my battery pack mod if you wouldn't mind guys.

I have a jump starter battery pack much like the yellow ones seen on ebay. It says it has a 12v 17ah battery, but the battery states 13.8v standby use. I have removed the jump leads, and left the 2 wires from the battery to the small pcb. This might be the charging circuit.

I have added a second cigar lighter type socket so that I can power the mount and plug in my Synguider as well.

I have also installed 2 dimmers inside to power the dewstraps, and installed 2 rca connectors to plug the straps into.

Now for the electrics.

To provide power to the 2nd cigar lighter socket thing, I just spliced into the red and black wires that went to the first one, assuming that if there is a 12v feed to the first, there will now be a 12v feed to the second.

The problem now is where to connect the leads from the dimmers. Can I connect directly to the battery terminal, or do I need to go through the small pcb.

If anyone has any knowledge of these battery packs and understands anything I have written, I would appreciate your help.

[malc-c]

Just take the feed for the dimmers off the back of the lighter sockets in the same way as you spliced the other socket in... Take a look at the diagram I posted a couple of posts back, but substitute the 12v input for your battery terminals... if that makes sense

Something like this

[allcart]

I did see your diagram a few posts back, but it was over complicated. Much more than I needed.

The diagram you just posted is exactly what I need. Thanks Malc.

[Islander]

Don't forget to stick a fuse in line with the dimmer circuits. A lead acid battery can dump a lot of current in a fault condition and you'll need to protect against this.

[Gina]

Yes, a fault can result in hundreds or even thousands of amps and the wiring catching fire. Lead acid batteries can be very dangerous indeed and have been a common cause of fires. Treat with great care end respect.

[allcart]

Thanks guys, now you have me worried. I shall indeed install a fuse or two.

[Gina]

Don't get too alarmed but I would suggest disconnecting the battery when you're not present until you get things fused, just to be on the safe side. The chances of failure and it causing a fire are pretty remote but if these things didn't happen at all we wouldn't need a fire brigade.

[lifeonmars]

Hi to everyone just started the LED dimmer project ,and for a non electronics person I am quite enjoying it.I only have the one LED dimmer at the moment ,but intend building a controller with four units in,

Can I ask some advice from the electronics buffs on here please ,the wires going from the little connecter on the board to the back of the pot are ever so fragile and guess what two have come adrift at the same time,can I extend these wires with some speaker wire and resolder them onto the pot,will the bigger wire cause any problems to the working of the unit? and number two anyone got a diagram showing the pot wiring in relation to the correct orientation of the plug,because two wires have come adrift I am not sure which way round they are(what a Plonker)I haven`t got a second unit to compare it two until the other three arrive.Thanks for all your help with this,if anybody can Thank You

[malc-c]

It won't matter, I would use thinner equipment wire, but if all you have is multi-strand speaker cable then that should be fine. On the POT you should connect one wire to the middle pin (the wiper) and the other wire to either of the other pins. If you find afterwards that the dimming is back to front (ie it starts bright, but fades as you rotate the knob, then swap the outer wire on the pot to the other side but leave the one attached to the middle pin where it is.

[lifeonmars]

Thanks for that information Malc thats much appreciated,trouble is with me I am learning as I go along with this,so yes its the middle and end one thats come off,seems to be very flimsy and I will make the wires longer to help gain access to the box ,but very grateful for your help

All the best Frank