Digital thermometer with 90s2313 and DS1820

[pasicr]

Hi for all,
I made this thermometer (sch is attached), work fine with 13mm common anode display,
question is:
I need to use Hi-Red 60mm CA 7-Segment LED Display,
is enough only to use +V = 12 V on switching transistors emiters (Q1 to Q4), and replace them with some superior transistor,
regards

 

[mostafahk]

no my freind , its not enough
also my english is poor

if you connect emiter to +12 your transistors always be on.
you must add 4 zener in base of transistors. same it
**broken link removed**

and now you have other problem:
your led's catods was always negative than anods( +5V < +12 ). so you have little light on all leds.
you must use 8 transistor as open collector on catods , or an open collector chip.

 

[viperpaki007]

This is another solution.....i have used two transitors instead of one.....as high logic from the mcu cannot cuttoff the PNP transitor because transitor biasing conditions are not fullfilled ....so one possoibilty is that to drive this transistor from NPN ...and give logic from the MCU to base of NPN....see diagram

 

[ilyasabdalnor]

pasicr
pleas the pdf file is not open
and i nedd u

 

[malponce]

I tried your solution for a common anode seven segment, but the first result was a pcb fill of fog, the NPN transistor burn, so I put a 1K resistor, and Bingo is working.