Is there some kind of trick to get the Quad D FF IC 74LS175 to work? I constructed this Breadboad 4-bit data latch. Switches are D1 D2 D3 D4 CLK and Clear from left to right. LEDs are Q1 Q2 Q3 and Q4 left to right. I checked the switches and LEDs separately, all work OK. But I get nothing when trying to work with the FF chip. Thank you!

 

Can you attach a schematic?

 

Can you attach a schematic?

 

But I get nothing when trying to work with the FF chip.

Clear is low active. Assuming you're not holding the clear switch down while depressing clock and holding one or more of the D inputs HIGH, that's why.

It looks like you're using 100 ohm resistors. That's far too small for the LEDs. I'd use 1k for the pull-downs and twice that for the LEDs.

 

/CLR is ACTIVE LOW.
You need to swap the pushbutton and the resistor for the /CLR input.

 

Clear is low active. Assuming you're not holding the clear switch down while depressing clock and holding one or more of the D inputs HIGH, that's why.

It looks like you're using 100 ohm resistors. That's far too small for the LEDs. I'd use 1k for the pull-downs and twice that for the LEDs.

Hi Dennis,

That's it! Works fine now. Thanks for your VERY FAST help.

Rich

 

/CLR is ACTIVE LOW.
You need to swap the pushbutton and the resistor for the /CLR input.

Thanks MrChips. Great help! and FAST too.

Rich

 

Use 100-220 Ω for pulldown and 1k-4k7 Ω for pullup.
74LS175 is TTL logic gates, not CMOS which can get by with higher value pullup and pulldown resistors.