L.E.D.`s - series or parallel?

[#1]

Hmm... not sure that I have a piece of ally that big ! ! ! ...but I get what you mean... and I can probably think of some odd bits of metal that could do the job of heatsink...

The wedge shape was based on how my arm would rest comfortably on it when writing... but I suppose I could probly make an internal wooden frame around the base line.. and make the far end of the slope/wedge a couple of inches higher to give an air gap below..

Thanks for all the help ... and the ideas... it`s going on the back burner while i cogitate things...

Watch this space...( nah... don`t do that... I`ll   @ you if and when an update is posted ! ! !>.)

cheers

[#2]

@shutter 

Not as efficient upside down but how about something like this in in the bottom of a ventilated box? https://www.ebay.co.uk/itm/UK-150mm-60mm-25mm-Heat-Sink-Aluminum-Heatsink-Cooling-Fin-for-Power-Ampl...

Whatever you do if you want a bright light you will get heat generated.

[#3]

@Baldrick1  OK... thanks for t he linky.... but that`s going on the expense side of "cheap & cheerful" home construction out of carrdboard and sticky tape ! ! ! ..

cheers

[#4]

@shutter 

Ah, I'd forgotten the Yorkshure roots!

Maybe you could fabricate something similar from a used Pilchard tin? It's the principle of reducing the spot temperature by spreading the heat to a larger area heatsink radiator and ventilating the box to transfer the warm air from the warm heatsink out of the box through convection that I was trying to get over.

[#5]

Yay !... Like I said.. will have to see what suitable bit of metal I have.

Cheers

[#6]

@shutter 

I obviously had a mental block the other day and failed to mention Plan B. This is to control the brightness and power dissipation with a mark space dimmer a.k.a an astable multivibrator with a suitable mark space ratio to get the brightness at a better level. These are sold to work with LED strips but cost folding money.

You should be able to knock one up within your Yorkshure budget with a 555 timer chip (30p), a power transistor and a few resistors and capacitors. PM me if you want an anorakal explanation.

[#7]

@Baldrick1   Hmm.. an interesting project.... use 555 timers a long time ago, when making practice oscilator(s) for morse practice... and also , I think , as an amplifier for a crystal set...

but not sure about that use  ? ? ? 

From my experiments with 1.5v cells  I don`t think there would be much difference in the brightness... and , in a way.. .that`s not the main problem now... as I can subdue that with an extra sheet of "mottled" paper, which works well enough for me to still be able to see the lines to write on....

the main problem is the heat factor, .. and I`ll have a dig around the shed and see if I can come up with some suitable metal... there`s a possibility I may be able to construct some kind of cooling/circulation fan.  I have some very small motors that I could adapt and make some blades for .... either fan or rotary... ... another interesting project... 

Thanks for continued interest..

Circuit diag for what you suggest would be useful, as I could knock that up and see if it works.

cheers

[#8]

@shutter 

I will knock up a circuit diagram when I have a bit more time.

The reason that you have not had any success with lower battery voltage is that once the applied voltage drops to the knee voltage of the LEDs then the LEDs go out, result misery.

What I am suggesting is that you apply the full voltage to the LEDs but switch this voltage on and off at a high enough frequency that the natural persistance in your eyes (this is the key point) don't notice any flicker. So for example if you switch the LEDs on and off with an equal mark-space ratio, applying the full 12v every time the switch is on at say 1kHz the persistance of your eyes should give you about half the brightness and there will be half the heat dissipation because the LEDs are on at full brightness for only half the time. This is how commercial LED strip dimmers work.

[#9]

@Baldrick1  Ah yes, of course... hence the "timing" circuit...

OK ... no rush on the circuit.... as you know, this is an ongoing project... and just something to do, when naff all going on... so definitely no rush..  Thanks.

[#10]

@shutter 

PM sent. I suspect that there's no way of attaching a spreadsheet in .xlsx format to either posts here or PMs.

[#11]

@Baldrick1   Just answered the PM  Thankyou...