Hi,
I agree...
additionally:
* U10 switches a node to GND
* U9 switches the same node to +5V
if both U9 and U10 are ON at the same time it causes short circuit and some smoke (at least)..
As for U10, it charges C8 quickly when the circuit powers up,
means it pulls the node to GND at power up ....
may I ask why you connect C8 to +5V?
If you connect C8 to GND you have the expected power up behaviour ... but without the need of U10.
Generally I´d say to use a cpacitor referenced to +5V (or any other voltage than GND) has to be ssen as critical.
The problem is: GND is considered as "THE REFERENCE" with no noise, zero volt.
But any other voltage will carry noise and will drift.
As long as you know this ..... and did the design for these errors .. it is OK.
But your circuit does not care for these errors.
Example: U5. The one input is "noise wise" coupled to GND. The other input is noise wise coupled to +5V. Thus a glitch in +5V will cause a glith in the output (= malfunction). As soon as you connec a capacitor in parallel to R17 both inputs are referenced to GND and are way more robust against malfunction.
****
in a circuit you have a signal flow ... from any input ... to any output.
If you don´t get the expected output ... then just trace the signal back in direction to
the input to find where the signal is like expected and where it is not like expected. That´s a simple task with a simulation tool. Just use it.
when the output of comparator U5 is high, U9 will charge C8
No. In this case there is no current through U9.
No current --> no charge
Klaus