[VicPiMakers Projects] LED and Flourescent tube voltages

[Deid Reimer]

And I found changing batteries in a couple of ups units challenging. 

Good work George. 

⁣Deid
va7rei​

On May 9, 2022, 2:08 p.m., at 2:08 p.m., Eileen <cody.eileen at gmail.com> wrote:
>Good detective work. 
>
>Eileen 
>
>Sent from my iPhone
>
>> On May 9, 2022, at 10:47 AM, George Bowden <gtbowdeng at gmail.com>
>wrote:
>> 
>> 
>> Well, I survived.  But these LED tubes need a ballast to produce a
>higher voltage than 110v.  The internal capacitors limit the current
>way too much.  Replacing the capacitors with a single 0.1 uF capacitor,
>for current limiting, allowed the dim output I desired.  But you have
>to get inside the bulb to do that, and the tube is made of glass...
>> 
>> 
>> 
>>> On Sun, May 8, 2022 at 11:30 AM George Bowden <gtbowdeng at gmail.com>
>wrote:
>>> If anyone has some ideas on LED and fluorescent tubes, pile in.
>>> I got some LED T8 tubes that are for direct replacement with
>fluorescents connected to instant on ballasts.  
>>> I carefully looked up ballasts that are compatible to this LED tube
>and chose to look at wiring diagrams for a B132IUNVHE-N ballast
>>> Clearly, the two pins at each end are joined together.
>>> 
>>> I then took apart one LED tube and drew its schematic. The
>electronics are repeated at each end of the tube (drawn one above the
>other), which makes sense because tubes can be inserted in either
>direction. I then drew AC power connections per the diagram above. Pins
>1 and 2 are at one end of the tube, and pins 3 and 4 are at the other. 
>Given the shorting of pin1 to 2 and pin 3 to 4, capacitors 1,2,6,&7 are
>shorted out, as are resistors 1,2,3&4. Not shorted are the capacitors
>and diodes next to each other.
>>> Tubes also could be inserted into ballast wiring where pin1 and pin2
>are not shorted, and it is interesting to have a tube design that must
>work with 4 different power connections!!
>>> 
>>> 
>>> 
>>> Simulating this design in LTspice shows 70v peak across the bank of
>leds, with current through each bank at 3.6 milliamps.
>>> There are actually 3 banks connected in parallel of 22 leds
>connected in series. I've only shown one bank.
>>> I've guessed at the surface mount capacitor values, and the
>simulation does not include the loads of LED bank2 and bank 3, so it is
>not quite realistic.  Also, I am guessing at the LED type.
>>> Given that ballasts try to maintain a certain current, using a 110v
>AC input is probably wrong, but that is what I will use to power the
>tube.
>>> I might include a 1.5uF 250v cap on the input to limit current, but
>the simulated current through the LEDs is very low already...
>>> My application is for a very weak light over my keyboard, so 3.6ma
>might be fine.
>>> 
>>> 
>>> 
>>> Now to plug it in....AAGGGHHH
>>> 
>>> -- 
>>> George Bowden  250-893-7423
>>> Victoria BC
>> 
>> 
>> -- 
>> George Bowden  250-893-7423
>> Victoria BC
>> -- 
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>
>
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