[Moved] very LOW brightness In digital voltmeter with ATMEGA8

[trm33]

I have designed Digital voltmeter with atmega8 but with only 3 resistors connected to common wires of 3 seven Segments, while all other 8 pins (a-h) are directly interfaced with atmega8. but this shows very low brightness. can we use transistors with all common wires are some other changes are necessary. any suggestion

 

[FvM]

Re: very LOW brightness In digital voltmeter with ATMEGA8

As a first point, you'll want current limiting resistors per segment to get constant segment brightness independent of the number of activated segments. In addition, it's often necessary to use a stronger digit driver than µC output pin, e.g. a transistor.

 

[milind.a.kulkarni]

Incase if you are using common cathode seven segment display then use individual transistor collector pins connected to the common pins and use transistor as a switch in CE configuration.... And control the switching of transistor using micro-controller such that you can multiplex the segment ..... I suggest you to put your circuit on the forum for better answers....

Good luck

 

[mathespbe]

LED brightness variation is depends on the current flow though LEDs. It may need pullups... Try transistor pullups for individual segment...

 

[Venkadesh_M]

Yeah post your circuit here for better replys , How many digits you are using?? If you used more digits in multiplexing you will loose the brightness, increase the ON time for each segment to full up the total period..

 

[trm33]

i M USING Common Anode configuaration, circuit is attached

 

[Venkadesh_M]

Remove the 220Ohm in a,b,c side and put them in 8 outputs... If controller output current doesnt supports, put separate Transistors....

 

[trm33]

Remove the 220Ohm in a,b,c side and put them in 8 outputs... If controller output current doesnt supports, put separate Transistors....

Now it works great

thanks