Increase the intensity of white led

[Muhammet TAN]

Posted on April 04, 2018 at 17:29

Hi , I want to drive White Led 7 Segment Display. MCUs power supply is 3.3V (STM32F030C6T6), and white led voltage about 2.8V when the current is 20mA. So, light intensity is too low. Is there any way to increase intensity or need to use STM8S005C6T6 ? 

[Tesla DeLorean]

Posted on April 04, 2018 at 19:29

Could you use a buffer capable of delivering more current?

[Muhammet TAN]

Posted on April 04, 2018 at 20:27

I have only a ULN2003APW but 7 segment display is common cathode. the company do not use buffer like 74hc series or cd4511. 

[T J]

Posted on April 05, 2018 at 00:42

You can use a transistor, good for upto 1 Amp.

or a FET good for 80A.

[Muhammet TAN]

Posted on April 05, 2018 at 07:26

Actually we've thought this. So there are so many component on the board. because there are three 7-segment displays. maybe using stm8 is more useful than stm32 for this circuit. 

[T J]

Posted on April 05, 2018 at 07:42

MM5450  in the old days,

or

https://www.digikey.com.au/product-detail/en/sparkfun-electronics/COM-11442/1568-1346-ND/5824095

 

currently.

[Muhammet TAN]

Posted on April 05, 2018 at 08:00

they are too expensive. we'll sell 400 or 500 of this card per year.  we want minimum component, minimum price and maximum performance. stm32 is more useful and easier software interface than stm8. I still believe that there must be a way to use stm32 with minimum component and price. I will continue the research about this.

[T J]

Posted on April 05, 2018 at 08:10

use a higher power supply on the digit drive,connected by a PnP and a zener per digit.

use the 2003 on the processor

[Muhammet TAN]

Posted on April 05, 2018 at 09:55

This advice is acceptable. But i will drive total 8 digit. 8 digit means 8 pnp,8 zener and 8 resistors. 

[T J]

Posted on April 05, 2018 at 10:30

yes, but you can get complimentary drive chips for that, I could only find 4 channel

https://www.digikey.com/product-detail/en/on-semiconductor/MMPQ2907A/MMPQ2907ATR-ND/458887

 

still going to need the zener and resistor in all 8 channels