| ??? 08/22/05 18:13 Read: times |
#99852 - analog voltages Responding to: ???'s previous message |
Hi Sunil,
I am pretty sure that there is more than just a P0 output, a LED segment, and a transistor controlled by a P2 output in line. There surely is a series resistor that limits the current during the "on" phase. I assume that 7 of these resistors are connected between the P0 output and the (combined) kathodes of the LED. Assuming that the transistors connect the common anodes to 5V during the "on" phase of each display segment, the level of the kathodes of the enligtened LED will be in the range of 2.5 to 3 V. If you connect the kathodes to 4081 inputs, the level may always be above the threshold voltage and so you will read a high level in all cases. So, be sure to connect the 4081 directly to the outputs of the first controller. Maybe you should use an oscilloscope to see what levels you have to deal with, just like Russell proposed. Harald |
| Topic | Author | Date |
| 7 segent data bus tracker | 01/01/70 00:00 | |
| Logic levels | 01/01/70 00:00 | |
| Pull up P0 and use 4081 | 01/01/70 00:00 | |
| I don't think you understand the issue | 01/01/70 00:00 | |
| logic o | 01/01/70 00:00 | |
| required steps skipped | 01/01/70 00:00 | |
| analog voltages | 01/01/70 00:00 | |
Harald Erik | 01/01/70 00:00 |