W
WW
- Jan 1, 1970
- 0
Hello,
I have a bread board and a 4xAA battery pack, I'm just getting started,
learning about electronics and wanted to try playing around with some
simple gates and switches.
I have connected the red lead to the top line of the breadboard, and
the black lead to the bottom, testing with a multimeter i get about
4.99v.
I then put the DM74LS08N chip on the board, it's a national
semiconductor chip, so i went to their website and found the chip
datasheet, it says pin 7 is ground and pin 14 is VCC so i assumed that
pin 1 was the pin under the little circular marker and set power and
ground accordingly.
For fun, i thought i'd test setting the output from pin 11 to an Led
but the Led lit up. I didn't expect this, i checked with the
multimeter, at pin 14 the voltage is 5.03, at pins 13 and 12 (which
aren't connected to anything), the voltage is 1.70v at pin 11 the
voltage is 4.30 (this is one of the gate output pins), which is turning
the Led on (I figure)
If I connect pins 13 and 12 directly to ground the gate behaves as
expected, but why is there voltage on these pins when the breadboard
holes aren't connected to anything.
Should the pins have voltage when not directly connected to anything?
Am i missing something in my circuit setup?
I tried hooking up a switch, it has 8 switches on it , i set the first
two input to Vcc and their outputs to the input pins of the DM74LS08N
but when the switch is outputing 0v the input pin to the chip still has
1.7v (the output pin from the switch has 1.7v too, but if i disconnect
it from the chip it has 0v.
I hope my explaination makes sense,
if there is a better forum/group to ask these questions in please let
me know,
Thanks,
Wilma
I have a bread board and a 4xAA battery pack, I'm just getting started,
learning about electronics and wanted to try playing around with some
simple gates and switches.
I have connected the red lead to the top line of the breadboard, and
the black lead to the bottom, testing with a multimeter i get about
4.99v.
I then put the DM74LS08N chip on the board, it's a national
semiconductor chip, so i went to their website and found the chip
datasheet, it says pin 7 is ground and pin 14 is VCC so i assumed that
pin 1 was the pin under the little circular marker and set power and
ground accordingly.
For fun, i thought i'd test setting the output from pin 11 to an Led
but the Led lit up. I didn't expect this, i checked with the
multimeter, at pin 14 the voltage is 5.03, at pins 13 and 12 (which
aren't connected to anything), the voltage is 1.70v at pin 11 the
voltage is 4.30 (this is one of the gate output pins), which is turning
the Led on (I figure)
If I connect pins 13 and 12 directly to ground the gate behaves as
expected, but why is there voltage on these pins when the breadboard
holes aren't connected to anything.
Should the pins have voltage when not directly connected to anything?
Am i missing something in my circuit setup?
I tried hooking up a switch, it has 8 switches on it , i set the first
two input to Vcc and their outputs to the input pins of the DM74LS08N
but when the switch is outputing 0v the input pin to the chip still has
1.7v (the output pin from the switch has 1.7v too, but if i disconnect
it from the chip it has 0v.
I hope my explaination makes sense,
if there is a better forum/group to ask these questions in please let
me know,
Thanks,
Wilma