quick update on my DIY LED lamps
- Thread starter 02GF74
- Start date
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OP
OP
02GF74
Über Member
copper tube was chosen since it conducts heat well, is easily & cheaplyl available and easy to work with, plus can be soldered to make more complex structures.
in first photo - thing nearest the screwdriver - you see a "thimble" made from a disc of copper with tabs cut to allow the edges to be folded over. These contact the tube and this is the heat sink as well as the tubing itself.
I've had the emitter running on a 5 V supply and it gets warm but not excessively.
just been downstairs to measure:
i = 480 mA
Vf = 3.7
so power dissipated is 1.8 W.
this will go up when I connect to 7.2 V RC battery. the driver max is 700 mA so with a 3800 mAh battery would give me a run time of 2.7 hours (two lamps) which is enough for the daily commute - charge battery at work. (I have two batteries on order)
in first photo - thing nearest the screwdriver - you see a "thimble" made from a disc of copper with tabs cut to allow the edges to be folded over. These contact the tube and this is the heat sink as well as the tubing itself.
I've had the emitter running on a 5 V supply and it gets warm but not excessively.
just been downstairs to measure:
i = 480 mA
Vf = 3.7
so power dissipated is 1.8 W.
this will go up when I connect to 7.2 V RC battery. the driver max is 700 mA so with a 3800 mAh battery would give me a run time of 2.7 hours (two lamps) which is enough for the daily commute - charge battery at work. (I have two batteries on order)
Panter
Just call me Chris...
- Location
- Sittingbourne, Kent
Looks good 
Which LED unit are you using for this?
Which LED unit are you using for this?
Just as a sideways slant.
The 2.3 - 3.0 Watt LED out of the Tesco torch can be epoxy resin mounted into a standard 'Flange bulb' case.
I did this technique with a Panasonic Ultrabright red LED ( 3000 mcd ) for a rear lamp in 1995ish.
But watch out if you try it for front lamps. You have to 'heatsink' the LED in a METAL lamp to get the heat away.
But I find the Tesco torch adequate without alteration,
The 2.3 - 3.0 Watt LED out of the Tesco torch can be epoxy resin mounted into a standard 'Flange bulb' case.
I did this technique with a Panasonic Ultrabright red LED ( 3000 mcd ) for a rear lamp in 1995ish.
But watch out if you try it for front lamps. You have to 'heatsink' the LED in a METAL lamp to get the heat away.
But I find the Tesco torch adequate without alteration,
OP
OP
02GF74
Über Member
The LED is a Seoul P4 star emitter.
a brief update. got my 7.2 V Ni-MH RC batteries from Honk Konk, charged them up and took some measurements.
The current drawn by the driver circuit diminishes as the voltage goes up; at 5 V is is around 490 mA, at 7.8 V it is down to 350 mA *. In layman terms it means a longer burn time when on the Ni-MH. A quick sum indicates that I can run two lamps, as inted, for 5 hours.
* if you do the sum, the power consumed is the same but as volts go up, amps go down.
hopefully finish them off this weekend.
a brief update. got my 7.2 V Ni-MH RC batteries from Honk Konk, charged them up and took some measurements.
The current drawn by the driver circuit diminishes as the voltage goes up; at 5 V is is around 490 mA, at 7.8 V it is down to 350 mA *. In layman terms it means a longer burn time when on the Ni-MH. A quick sum indicates that I can run two lamps, as inted, for 5 hours.
* if you do the sum, the power consumed is the same but as volts go up, amps go down.
hopefully finish them off this weekend.
fossyant
Ride It Like You Stole It!
- Location
- South Manchester
Clever bugger...I have a habit of frying stuff if I mess with anything..... 
gbb
Squire
- Location
- Peterborough
02GF....are you building this from a plan ? I assume the LED needs a driver ?
I fancy a go at something like this..have you got a build list or plan you'd care to share ?
I fancy a go at something like this..have you got a build list or plan you'd care to share ?
OP
OP
02GF74
Über Member
I guess you could use a drop resitor but that wastes energy. I am using a driver. I looked into making my own but it was not cost effective - i.e. I could buy ready made and tested drivers from China for much less which are on double side boards so very compact. I plan to fit another large diameter piece of tube to house the driver and waterproof switch in the "lamp" body.
search for seller: sureelectronics and item Driver <--- linky
there is no plan but the idea is to do it a much reduced cost - these Lamps are being sold for close to £ 200 when I last looked.
My lamps should give something like this
a good run for the money. Hope Vision Single LED £ 90 RRP.
.... but the drivers I am using are a bit under powered for the emitters i.e. I could push more power into them thus get more light; that may be the next project once I have this one done.
search for seller: sureelectronics and item Driver <--- linky
there is no plan but the idea is to do it a much reduced cost - these Lamps are being sold for close to £ 200 when I last looked.
My lamps should give something like this
.... but the drivers I am using are a bit under powered for the emitters i.e. I could push more power into them thus get more light; that may be the next project once I have this one done.
OP
OP
02GF74
Über Member
oh, buttockss.... 5 W driver just found thjese on the bay of E; now I want ....... good price too......
gbb
Squire
- Location
- Peterborough
02GF74 said:
02G...i'm in the process of building a 3w LED lamp myself...can i ask...
Single LED requires 3.7 v...5v max (IIRC)
The drivers i've seen are rated at 3-30volts (or thereabouts)
I assume you have to put in the correct voltage (ie 3.7 to 5 volts in my case), and the driver 'smooths it out'. Am i right in that sense ?
Can you get away without using a driver....what is it supposed to do ?
You're quoting a 7.2v battery....too much for a single LED isnt it ?...but then i see you're thinking of running two LEDs.
I'm ok at the mechanical / assembly side, but the electronics leave me a bit all over. Questions questions
OP
OP
02GF74
Über Member
ok, so you know a bit about how LEDs work and about the forward volt drop.
as you say, if you are connecting to a constant voltage supply, you would put in a resistor (known as drop resistor) to limit the current in the LED. The value of the resistor is simply the supply voltage less Vf divided by current.
Connecting a LED directly to a voltage source almost certainly will damage it as there is nothing to limit the current going through it, hence the drop resistor.
Depending on the colour of the LED., Vf will be different and varies from around 2.5 V to 3.5 V.
The major drawback with using a drop resistor is that you are wasting power, given off as heat.
The driver circuits use electronics to provide a constant current to the LED and can be connected to a range of voltages. They are very efficient so you are converting a hell of a lot more battery energy to light rather than heating up air.
I connected the 5 W driver - smaller than the Chinese version - and doing calculation of battery voltage and current drawn, taking into account driver efficiency - quoted at 80%, they deliver > 4.5 W to the LED. The LED definitely appears to be brighter than when using the 3 W driver.
The assebly is easy - solder two wires for the battery and two to the LED - instructions are clear on how to do this.
there is a third control wire that can act as a dimmer but I ain't gonna bother with that.
as you say, if you are connecting to a constant voltage supply, you would put in a resistor (known as drop resistor) to limit the current in the LED. The value of the resistor is simply the supply voltage less Vf divided by current.
Connecting a LED directly to a voltage source almost certainly will damage it as there is nothing to limit the current going through it, hence the drop resistor.
Depending on the colour of the LED., Vf will be different and varies from around 2.5 V to 3.5 V.
The major drawback with using a drop resistor is that you are wasting power, given off as heat.
The driver circuits use electronics to provide a constant current to the LED and can be connected to a range of voltages. They are very efficient so you are converting a hell of a lot more battery energy to light rather than heating up air.
I connected the 5 W driver - smaller than the Chinese version - and doing calculation of battery voltage and current drawn, taking into account driver efficiency - quoted at 80%, they deliver > 4.5 W to the LED. The LED definitely appears to be brighter than when using the 3 W driver.
The assebly is easy - solder two wires for the battery and two to the LED - instructions are clear on how to do this.
there is a third control wire that can act as a dimmer but I ain't gonna bother with that.
Amanda P
Legendary Member
- Location
- York. Well, York-ish...
I would like to refer the honourable members (who are obviously interested in this sort of thing) to this thread.
Fisha disappeared, but I have built several lights to his design and they are brilliant (pun intended).
Fisha disappeared, but I have built several lights to his design and they are brilliant (pun intended).
OP
OP
02GF74
Über Member
yes, I know about that but I ain't paying £ 9 for a box if I can make my own for free!
By the way, I tried the 5 W drivers - much smaller than the 3 W ones I got from China and definitely brighter.
just need to fit the on/off swtich plus figure out how to wire both up to the batter so that connection is waterproof.....
By the way, I tried the 5 W drivers - much smaller than the 3 W ones I got from China and definitely brighter.
just need to fit the on/off swtich plus figure out how to wire both up to the batter so that connection is waterproof.....
