Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

problems getting M74HC259B1R to work

777xxx

Member
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?
 

Attachments

  • Untitled1.png
    Untitled1.png
    4.6 KB · Views: 73
Everything’s wrong. Start with a more accurate schematic with part numbers , correct polarity, bias resistors , no floating inputs , and a better question
 
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.

1711159333068.png

1711159896307.png
 
Last edited:
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.

View attachment 145082
View attachment 145083
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?
 
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?
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.
 
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.

View attachment 145082
View attachment 145083
its not working unfortunately. the light comes on when i press the button but it doesnt latch
 
Then you are using the wrong chip. This is a Latch with Data thru enable Low
1711526778548.png
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.
 

Latest threads

New Articles From Microcontroller Tips

Back
Top