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So I went to RadioShack recently because they were having a 40-80% off liquidation/closing sale. I picked up quite a few things, and one was a 555 timer for a decent discount from its already low price. Now, I'm about to make an online purchase and I don't know which one it was. It was either the tlc555cp or the ne555p. So, two questions arise: What are the differences in pinout/internal circuitry the would make them different, and are there any such differences? Thanks!

EDIT I'm home now. I see it's a TLC555CP. What are the differences between that and the NE555?

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  • \$\begingroup\$ take a good picture (so the writing is clear) of the top of the chip. \$\endgroup\$ – pgvoorhees Oct 8 '16 at 2:25
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The TLC is a newer version using a different type of semiconductor technology. The NE is a TTL chip while the TLC is a CMOS chip. It has different VIL/VIH/VOL/VOH and VDD levels, as well as IOL and IOH. As such, the TLC version cannot accept as high a voltage as the NE version, and it cannot drive as large a load directly. But the benefit is a much lower IQ, or standby current. There is some other differences in timing and other specs, but That's the main difference for hobbyists on general projects.

This can all be learned from the datasheets for each chip.

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  • \$\begingroup\$ Ok. I have the tlc driving a 3.4v 50ma white led off a 9v battery. What difference between them would I notice in that application? \$\endgroup\$ – Bobdabiulder Oct 8 '16 at 3:17
  • \$\begingroup\$ Well. The NE can source or sink 200mA. The TLC can only source 15mA and sink 100mA. That means if you turn on the led by driving the 555 output high to the led anode and led cathode to ground, you will burn out the output. If you wire it with led anode to V+, and cathode to 555 output low, it would be the same to you. \$\endgroup\$ – Passerby Oct 8 '16 at 3:37
  • \$\begingroup\$ What does source and sink mean? I don't get your last sentence - is that a solution or are you saying there's no solution. The timing clock I'm using is fast - it's on and off 3 times per seconsd, is that ok? Would the NE be better then? It's certainly cheaper on ebay \$\endgroup\$ – Bobdabiulder Oct 8 '16 at 3:54
  • \$\begingroup\$ 3 hertz isn't fast. And I'm saying wire the output so that your led turns on when the output goes low is the solution for your set up. \$\endgroup\$ – Passerby Oct 8 '16 at 3:55
  • \$\begingroup\$ Ok, but would I be safer with an NE anyway? \$\endgroup\$ – Bobdabiulder Oct 8 '16 at 3:56
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Ok, I can answer myself now. Basically, the NE555 uses much more voltage than the tlc555cp. The tlc chip is a much more power efficient little chip that is better on your battery life.

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