Power supply voltage drop

[kinarfi]

I looked at you pictures and it's similar to what I have built, only I powered mine from 14.5vdc from a car.
With your 15 vac transformer, use a full wave bridge, then connect 2 or 3 strings of 4 LEDs with your LM350 in the current configuration, your transformer doesn't appear to be able to power 5 in series, so add or subtract 2 LEDs.
I assume you got your LEDs off the internet and they are very similar to these: Color temperature:6000-6200K, Forward Voltage: 3.0V~3.2V, Forward Current: 350mA.
The current through a LED is what counts, too much and they die, too little and they dim or go out. On these, hold the current at 350ma and they are happy and bright as long as you get rid of the heat.
OH YEA, The 3.57 ohm resistor need to be 1/2 watt, recommend 1 watt

 

[skmdmasud]

I looked at you pictures and it's similar to what I have built, only I powered mine from 14.5vdc from a car.
With your 15 vac transformer, use a full wave bridge, then connect 2 or 3 strings of 4 LEDs with your LM350 in the current configuration, your transformer doesn't appear to be able to power 5 in series, so add or subtract 2 LEDs.
I assume you got your LEDs off the internet and they are very similar to these: Color temperature:6000-6200K, Forward Voltage: 3.0V~3.2V, Forward Current: 350mA.
The current through a LED is what counts, too much and they die, too little and they dim or go out. On these, hold the current at 350ma and they are happy and bright as long as you get rid of the heat.
OH YEA, The 3.57 ohm resistor need to be 1/2 watt, recommend 1 watt

I did the constant current first using the LM350 and found out that its not efficient, produces huge heat. Not good for 8hr or 9hr straight. Then i made a switching led driver following this https://www.instructables.com/id/Poormans-Buck/?ALLSTEPS its a great design very efficient and easy to make. i made 4 drivers all works great i love it. As you see in the picture in the very left and right i have placed the driver and the LM350 is just there to feed 20V to the drivers.

The leds are from my local electric store i can buy 6 leds at $1 of course i pay in BDT not $.

have a look at this
View attachment 68207

I bought 10 leds without metal base(the aluminum coin like thing on which leds are mounted) + 2 round big aluminum plated on which i can mount 5 leds at only TK64 (~$0.80) ONLY

 

[kinarfi]

pretty sweet, You're using buck system basically similar to the constant current set up, I've done the same thing only boosting, using the feed back to control the voltage to so I get the correct current.

 

[skmdmasud]

pretty sweet, You're using buck system basically similar to the constant current set up, I've done the same thing only boosting, using the feed back to control the voltage to so I get the correct current.

Thats great. Can you please share your booting circuit, is it using LM350??

 

[kinarfi]

Thats great. Can you please share your booting circuit, is it using LM350??

I boost 12.6 to about 40v using a LT1270a, 10A switcher.

 

[Claude Abraham]

In series the current is the same, 350 mA, not 1.75A. The voltages add, the current is the same. Make sense?

 

[skmdmasud]

I boost 12.6 to about 40v using a LT1270a, 10A switcher.

I found datasheet of the regulator it is a good device. I couldnt find the price of this regulator, guess its expensive.

 

[kinarfi]

US Prices about $10.50

https://www.linear.com/purchase/LT1270

 

[skmdmasud]

US Prices about $10.50

https://www.linear.com/purchase/LT1270

for boost application 10$ is worth. Parts for my buck costs me around 3$ including pcb and it can handle 15A. I will see if its available in my locations.

Thanks and Regards

 

[kinarfi]

cheaper boost with constant current boost circuit and a previous thread where I got help.
https://www.electro-tech-online.com/threads/14-to-40-or-50-volt-boost-circuit.124138/#post1026371

 

[circuitspecialists]

HI
What are the LED specs (forward voltage and current)? The 1 W could refer to OPTICAL power, in that case electrical power
requirements will be much higher.

 

[skmdmasud]

cheaper boost with constant current boost circuit and a previous thread where I got help.
https://www.electro-tech-online.com/threads/14-to-40-or-50-volt-boost-circuit.124138/#post1026371

this boost circuit look very simple, good design. Did you test this circuit. The max input for the circuit is is 14V does the output changes with load?

 

[kinarfi]

cheaper boost with constant current boost circuit and a previous thread where I got help.
https://www.electro-tech-online.com/threads/14-to-40-or-50-volt-boost-circuit.124138/#post1026371

this boost circuit look very simple, good design. Did you test this circuit. The max input for the circuit is is 14V does the output changes with load?

This circuit is operating in a couple of couple of places, (one is on my work bench and powers 2 10v, 10W LEDs and gets varying voltages), be more specific in your question and maybe I can test it, but yes, I believe that as the load changes, the output voltage changes and current remains constant, and as the input voltage changes, the output remains constant. It is set up to keep voltage across the LM317 constant, which works, but I think it can be improved. If you want constant voltage, rearrange the output sensor so you monitor the out put instead of the voltage across the LM317.
When I built this circuit, my main concern was diode current, so I used LM317, second concern was LM317 heat, so I had to control the output voltage.