Clock, Step and Hold logic

Preamble

Following on from Sequence Dancing – Schmitt_trigger_NAND_implementation, and the number of issues with that schematic (from CMOS 4017 Based 8 Step Sequencer)…

clk_input

Basically, the HOLD function of the schematic above does not work:

  1. An inverted (inverted by the HOLD circuit debouncing Schmitt trigger – see below) active low button press to the HOLD control (i,e, where the input to the circuit above is active high),  does not hold, but, rather, enables the clock. The active low HOLD button press is inverted by the Schmitt trigger NAND gate (see schematic below), providing an active high HOLD input to the schematic above. However, this actually enables the clock, rather than holding it.
  2. A positive edge is created when the HOLD is released, thereby advancing the clock asynchronously
  3. If the active low button press is passed through an additional inverter, so that the input to the circuit above is now active low, then the action of pressing hold gives a rising edge clock, thereby holding on the subsequent step, rather than the current step..

Continue reading Clock, Step and Hold logic

Hermes destroyed my Fluke PM3092

Preamble

Wikipedia states that Hermes is the god of commerce, as well as trickery and thieves (amongst other things). The latter two might be best to describe Hermes – the courier company. In fact Perses would be a more suitable name for the company, as he is the god of destruction.

I had purchased an absolutely beautiful Fluke PM3092 oscilloscope, and was really looking forward to receiving it. When it arrived, in fact before it arrived, before I had even opened the door I heard the delivery guy drop the package on the floor. “That doesn’t sound good”, I thought to myself. When I opened the door, I said, immediately and with a glare, that the package was an oscilloscope and that it needed to be handled carefully. The guy’s face fell. “Ah well”, he cried, as he departed, “Have fun with it!”

Continue reading Hermes destroyed my Fluke PM3092