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Advice on modifying LED light circuit

nate72

Jul 18, 2022
2
Joined
Jul 18, 2022
Messages
2
Essentially, I would like to disable one set of LEDs on a photography light. They are on a separate circuit to the best of my understanding. The light controls go through the series of contacts at the bottom. The direct power goes through a power plug on the side (shown on the far left in the image).

Background:
I have an LED light set for streaming that allows the user to adjust the light temperature. It does this by having two 'separate' circuits of LEDs side-by-side, one warm and one cool.

For my uses, I only need the cool LEDs. Generally, I can dial those in with the light controls. However, the individual light panels can also be connected directly, and in that case, both sets of LEDs run at full power and are not adjustable. I would like to disable the warm LEDs so that only the cool set run when connected directly.


compare-lights.jpg back-front-circuits.jpg
 

CircutScoper

Mar 29, 2022
300
Joined
Mar 29, 2022
Messages
300
temp.JPG
Essentially, I would like to disable one set of LEDs on a photography light. They are on a separate circuit to the best of my understanding. The light controls go through the series of contacts at the bottom. The direct power goes through a power plug on the side (shown on the far left in the image).

Background:
I have an LED light set for streaming that allows the user to adjust the light temperature. It does this by having two 'separate' circuits of LEDs side-by-side, one warm and one cool.

For my uses, I only need the cool LEDs. Generally, I can dial those in with the light controls. However, the individual light panels can also be connected directly, and in that case, both sets of LEDs run at full power and are not adjustable. I would like to disable the warm LEDs so that only the cool set run when connected directly.


View attachment 55652 View attachment 55653

Only guessing, of course, but perhaps "W_PWM" stands for "White _ Pulse Width Modulation" (i.e. cool LEDs) while "Y_PWM" is "Yellow _ Pulse Width Modulation." (warm LEDs).

If my guess is correct, then cutting "Y_PWM" (e.g., with an added switch) would disable the warm LEDs.
 

73's de Edd

Aug 21, 2015
3,436
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Aug 21, 2015
Messages
3,436

Sir nate72 . . . . . .
(are you really 72 YO . . .or only going on 50'ish ? )

Mark up Photo . . . . . . . and . . . . . Concept of Circuit Design . . . . . . as per my perception . . .
( Frame . . . . . 24 K gold foil flakes and Brazilian Rosewood . . . hand rubbed )

upload_2022-7-19_5-44-51.png


HOLY MACKERAL . . . . dere Andy ! this boards opaque white reeeeeeeeee-sist is on par with a Macbook's damn BLACK resist covering, one can't make out its underlaying foil traces ANYwhere . . . only the vias !

This is a job for your multimeters lowest ohms function . . . to detect direct connections.
SINCE . . . . .we need to know about a couple of direct connections.
I am seeing the 5 VDC power supply coming into the USB connector and feeding the RED BOXED in circuitry, which uses U3 and rings L1 inductor and D1 back EMF rectifier , to then up vert that 5 V DC input, on up to 24-30'ish volts DC to be then stored in E-cap C6 at the very bottom. That powers up the LED LIGHT strips.
That power then us routed up to individual sets of U4 and U7 LED controllers ( BLUE BOXED) for your WHITE and OFF WHITE LED illumination strings.
They keep their operating voltages and current control in check.
An educated guess is that the individual very bottom . . .YES . . .Pulse Width Modulated control lines coming in at the very bottom, will then route up to ?R3?R8? and R17 and pass upward out of them to the separate bases of Q6 and Q5 transistors (VIOLET BOXES) . They will then respectively and proportionately control the two strips of ILLUMINATOR LED's.

HOMEWORK . . . .
Get metering and place in its lowest ohms range, short the meter probes to see what the display reads, when being as a full / dead short connection.
Move over to the UNPOWERED AND UNPLUGGED light unit to measure from the bottom incoming Pulse Width Modulated connections and see if they are then routing up and direct connecting into the bottom connections of those just referenced resistor pairs. Then see if their top connections don't then route up to the bases of Q5 and Q6 control transistors ?
Next, we need to see those transistors positons within the circuitry, the most logical would be for the emitter of those transistors to go to ground. Measure from either emitter down to bottom E-caps right ground lead of C6, to see if there is direct connection..
ARE the emitters going to ground ?

If so then you just need to differentiate as to which transistor controls the off White LED light string and disrupt / open its driver transistors base drive voltage .
AND as hard as that . . . . . white resist encased . . . . . foil trace might be to locate, I, myself, would go for having my mini SPST switch mounted and then , have its wiring then shorting out base drive with a connection to the EASILY accessible base and emitter of that involved driver transistor.

73's de Edd . . . . .

I was wondering why the Frisbee coming at me kept getting bigger and bigger and BIGGER . . . . . but then it hit me.


.
 
Last edited:

nate72

Jul 18, 2022
2
Joined
Jul 18, 2022
Messages
2
Sir nate72 . . . . . .(are you really 72 YO . . .or only going on 50'ish ? )

The latter. See the thing is, I am scheduled to learn electric circuitry when I reach 70. So until then, my skills with a volt meter and probes could probably still save the world from a dangerous ticking device, but only with someone like you on the other end of a video call telling me what goes where to stop it. ;)

You might wish to throw a satellite (NASA?) at my head for asking such an electrically-boorish question, but if I were to scratch off one of the yellow LED's like an old scratch-and-sniff sticker, would that break the circuit, or is there probably a bypass circuit leading to the next LED anyway?
 
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