12v DC supply for 5v and 7v loads on PCB.... direction needed

Thread Starter

johnaustinkaty

Joined Jul 16, 2021
37
I know it's scary, but that's doing my best.... I need someone to help me make sure this is ready for
making a few PCB's. I tried to label everything. Yes, I will pay for your time
;). Thx again.
-John
 

LesJones

Joined Jan 8, 2017
3,654
R set is the resistor that sets the output current on the AL8843Q. It is connected between pins 3 and 6, See the application circuit on page 2 of the data sheet. See page 12 of the data sheet for notes on the choice of diode. See page 13 of the data sheet for notes on the inductor selection. (Many of the graphs on the data sheet are with an inductor value of 47uH so that would probably be a suitable value.) It will probably look similar to the one on the LD24AJTA module. (The one on that module is 470 uH)

Les.
 

Thread Starter

johnaustinkaty

Joined Jul 16, 2021
37
R set is the resistor that sets the output current on the AL8843Q. It is connected between pins 3 and 6, See the application circuit on page 2 of the data sheet. See page 12 of the data sheet for notes on the choice of diode. See page 13 of the data sheet for notes on the inductor selection. (Many of the graphs on the data sheet are with an inductor value of 47uH so that would probably be a suitable value.) It will probably look similar to the one on the LD24AJTA module. (The one on that module is 470 uH)

Les.
I forgot to put my .17ohm Rset resistor back in.....
I'll also follow your direction regarding the diode and inductor
thx
 

Thread Starter

johnaustinkaty

Joined Jul 16, 2021
37
I edited my schematic to put three .5 ohm resistors in parallel to obtain the required .17 ohm for my AL8843 circuit.
Is this arrangement correct?
I'm sure you guys are rolling your eyes, but I appreciate your patience.
1626842547921.png
 

Thread Starter

johnaustinkaty

Joined Jul 16, 2021
37
I am using LD24AJTA for now for testing amperage to my LEDs. I have my PWM signal connected to it from the ATTINY and 12v from a battery. My sketch was setting the PWM range from 0 to 255. With that, I was getting 860mA to the LEDs which was very bright and pushing the 900mA limit of the LEDs. I don't want to push the LEDs that high and shorten their life, so I have my Δ pulse width set to 220 now (adjusted in my arduino sketch). I'm getting a Δ amperage now of 740mA, which appears to be ideal as far as brightness and is 160mA under the max for my LEDs. I believe this might be my most efficient setup as the LD24AJTA board is very small and inexpensive.
I will post an image of my revised board when finished.
Thx again.
 

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