problems getting M74HC259B1R to work

7

777xxx

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im trying to get it to latch at address 0 to output 0. no joy. the light just stays on and when i press the button, it gets brighter. no on off latch. whats wrong here? any ideas?
 

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Everything’s wrong. Start with a more accurate schematic with part numbers , correct polarity, bias resistors , no floating inputs , and a better question
 
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777xxx said:
ok. is there a circuit diagram anywhere that i can look at which allows me to use this chip as a latch with press button switch?
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The datasheet is usually a pretty good place to start (along with a basic understanding of ohms law so you don't exceed the specified max current in/out of any pins.

 
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1. Observe all antistatic precautions
2. Never leave CMOS inputs floating. Either pull up or down.
3 Place a ceramic cap near IC V+ to gnd
4. Latch Enable =0 must be enabled.
5. Clear must be disabled = 1
6. Output is immediate until Enable = 1 then it is latched in to register.
7. Then ABC address select = 000 to observe output on Q0 = 0 LED off = 1 ON
Your LED is backwards if grounded.
Vcc must be 5V +10% max.


 
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thank you for your diagram. i dont understand what you mean when you say 'led is backwards when grounded'. in my diagram the positive lead is connected to the data output and the negative is attached to ground. is this wrong then?
 
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777xxx said:
thank you for your diagram. i dont understand what you mean when you say 'led is backwards when grounded'. in my diagram the positive lead is connected to the data output and the negative is attached to ground. is this wrong then?
Click to expand...
It is absolutely WRONG! The output would have to be negative (below GROUND) in order to provide a positive (forward) bias to the diode. You also need a current limiting resistor in series with the diode.
 
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its not working unfortunately. the light comes on when i press the button but it doesnt latch
 
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Then you are using the wrong chip. This is a Latch with Data thru enable Low
which means disable high = memory latch

You want a different design that is edge sensitive to inputs but then there must be some read and reset function added.
 
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