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Problem with the HEF4008BP IC chip ?? Answered

i just bought a HEF4008BP 4 bit binary adder ic. I connected pin 16 to V+ and pin 8 and 9(Carry in pin ) to ground  and then set up a 8 way DIL switch with 10k and 1k pull down resistors to gnd and the switch  to the inputs of the adder.Then i connected the outputs of the adder to the positive of a 3mm led each separately  .The dil switches are all of but still all the led's light up once i connect the 9v battery . The chip can run off 5v-15v . Also there is no sign, name or logo of a manufacturer on the ic .Is this a fake ic or might i have possibly blown it or have i done something wrong .Please help me.

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iceng

5 years ago

Your wiring diagram is Correct on all counts.
The adder, the switches, the transistors and the LEDs.

Even the values are correct,
The 12 ma LED current with a 680 ohm series resistors and dip_sw pull downs.

If you have a picture of the actual breadboard maybe I could spot something.

If you have a meter or even use one of your LED transistors with base 47K as a probe.
And do around verify the adder input voltage levels to see if the outputs follow the  truth table.

Did you buy only one 4008 ?

A

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steveastrouk

5 years ago

See if the output circuit works without the adder chip.
Check that the chip really IS connected, using a meter. breadboards are very unreliable.

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steveastrouk

5 years ago

current limiting resistors on LEDS ???

DRAW circuit.

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Strontiumsteveastrouk

Answer 5 years ago

no not current limiting resistors pull down resistors for the inputs not for the led ,anyway here is the circuit:

4008_09.gif