Electronics > Beginners
4017 IC Driving LEDs Using Only One Resistor
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Zero999:

--- Quote from: Audioguru on September 15, 2018, 02:26:04 am ---How can your simulation program work when your schematic shows no supply voltage?
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It looks like Proteus, which I've used for PCB design, but not the simulation, as like LTSpice too much. I believe it's possible to high the power supply pins, in order to make the schematic easier to follow, but I agree it can be confusing too.


--- Quote ---Years ago I made some chasers using 74HC4017 ICs, Hewlett Packard 3.2V blue and bright green LEDs and powered from 6V. A problem was caused since only one current-limiting resistor was used for 10 LEDs. Some of the LEDs leaked current when they were reverse biased (only 2.8V of reverse bias) causing some of the other LEDs to dimly glow when they should be turned off.

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Yes, tiny leakage currents can be a problem with blue and green LEDs. Not only do they start to glow at very low currents, but the human eyes is more sensitive to the shorter wavelengths of the spectrum, at lower intensities. In some cases a high value resistor in parallel can help, but the obvious solution in this case is one series resistor per LED.
HandyAndy:
Sorry wasn't able to reply sooner.
That is in fact Proteus.
The VCC lines have 9V on them but for some reason Proteus hides that in its settings.  Might be set to hide it but I don't see why you would really want to hide that from view.
To share the simulation animation I used a program called ScreenToGif.
I hope I answered all your questions as you have answered all of mine as well as provided me with some great info.
Thank you all!   :-+
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