74HC Flip Flops are available at Mouser Electronics. Mouser offers inventory, pricing, & datasheets for 74HC Flip Flops. 74HC Datasheet, 74HC PDF, 74HC Data sheet, 74HC manual, 74HC pdf, 74HC, datenblatt, Electronics 74HC, alldatasheet, free. 74HC datasheet, 74HC circuit, 74HC data sheet: PHILIPS – Dual JK flip-flop with set and reset; positive-edge trigger,alldatasheet, datasheet.

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datasheeet I’m a complete amateur, I’ve probably gotten a datasheft things wrong with this already. I’m using an SN74HC dual j-k” flip-flop chip.

I’m trying to toggle the led forgot to add a resistor in the diagram, ah, also forgot to add a line from 5V to Vcc. When the circuit is powered, the led turns on but does not toggle when the momentary switch is pressed and released.

There are exceptions, with some circuits incorporating a built-in pull-up or pull-down resistor, but unless the data sheet mentions these, assume they don’t exist.

(PDF) 74HC109 Datasheet download

Leaving unused pins floating particularly with CMOS can produce amazingly intermittent, bizarre and maddening errors. And don’t think that you can ignore the inputs of an unused part of the circuit, such as the unused flip-flop in your 74HC Don’t even think about it.


Sometimes that works, and sometimes it doesn’t. Tie them all high or low. Caps are cheap and don’t take up much space, but the problems arising from not enough of them can be hard to diagnose.

Connect the cap directly to the sockets nearest the IC power and ground pins.

74HC109 DIP-16 J/K flip-flop

On the one hand, it will try to draw too much current in the on state, and will also clamp the output to a low voltage which datashewt input will not recognize as high.

In this case, a ohm resistor, combined with the LED voltage and the limited high output drive of the flip-flop will give you about 6 or 7 mA LED current when on. Just to show what I’m talking about, once you’ve got the circuit working, put an LED directly to ground on the flip-flop clock input, and watch what happens.

In this case, it will show up as intermittent operation of the flip-flop, depending on whether or not it got an even or odd number of contacts when you press the switch. For more complex circuits using counters or state machines you can get the most amazing errors. You are clocking a flip-flop directly from a switch that has not been de-bounced. You need a de-bouncing circuit to feed the flip-flop’s clock datasjeet.

As others have suggested, this could be a simple R-C network, or as a better option, use an SPDT change-over switch and a set-reset SR flip-flop as a de-bouncer. A common way to do this is with cross-connected NAND gates. By clicking “Post Your Answer”, you acknowledge that datasheett have read our updated terms of serviceprivacy policy dafasheet cookie policyand that your continued use of the website is subject to these policies.


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Maximum Low-Level input voltage with my Vcc at 5V is about 1. LED does not light up, I’ve done something wrong again haven’t I?

74HC Datasheet, PDF – Alldatasheet

Just pull it down to 0V with a single resistor! LED lights up but does not toggle.

Please build the following circuit: WhatRoughBeast 49k 2 28 Always connect the GND pin. Never leave it unconnected, even if the circuit appears to work.

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