I would like to modify your design,,to drive a 7 segment display,,that is build up of 6 or 7 leds per sement.Say 20 mA per led times 7...or 140 ma per segment...times 7...for the number 8...so aprox one amp. will the circuit work for this ampacity?
Two ,Questions,,,,If i had the leds in series for each segment,the draw will be way less,,,Is this a better idea? And second,,,the 2803,,i believe is a buffer...and all i know about a buffer is it will allow more current to flow?? Can you expain the concept of a buffer,,,thanks,,jon
1) So how would you wire the LEDs in series for each segment? They're wired internally in each digit display with all the anodes tied together.
2) Take a look at the datasheet for the ULN2803. It gives a functional diagram and a partial schematic. This is essentially a Darlington transistor array.
Do a websearch for "Wiki Darlington pair" to read a short description of what this is. The datasheet is here: focus.ti.com/lit/ds/symlink/uln2803a.pdf.
Here is a Wikipedia article on buffers: en.wikipedia.org/wiki/Buffer_amplifier.
Although this discusses buffer amplifiers in general, the ULN2803 is just optimized for use at 5V logic levels.
Hi,mike,,,I mean if i want to build my own seven segment display,,,made from say 10 leds per segment,,,would it be best to have the leds in series or parallal?....PS I have been working with a new product,,called cold neon,,,its leds in a tube,,,and it seems like they are in groups or series leds..that are all paralleled...any way...for my 7 segment display,,, i think it may be best to have the leds in series,,,untill i get over 4 ,,or 5 leds,,,if i am staying with 12 volts,,,then at that point to get to 10 leds I probably could add 5 more in parallel to that,,,what do you think..
Comments
Good job!
How about a 3 digit seven segment display for Phoenix ...
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How does the dp work, or how would you add one?
2) Take a look at the datasheet for the ULN2803. It gives a functional diagram and a partial schematic. This is essentially a Darlington transistor array.
Do a websearch for "Wiki Darlington pair" to read a short description of what this is. The datasheet is here: focus.ti.com/lit/ds/symlink/uln2803a.pdf.
Here is a Wikipedia article on buffers: en.wikipedia.org/wiki/Buffer_amplifier.
Although this discusses buffer amplifiers in general, the ULN2803 is just optimized for use at 5V logic levels.
· I used a rather unique high side driver for my high voltage 4 digit LED displays.
· Attached is a schematic.
Bean.
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