Hi,
I am driving a 7414 Schmitt Trigger from a PS2505 optotriac I have a 120VAC switch coming in to the PS2505, the output of the PS2505 going to a 7414 Schmitt Trigger and the Schmitt output going to an Arduino input pin.
I have triple checked that I have 5V at pin 14 and GND and pin 7 of the Schmitt. I ave also swapped out the 7414 for another one with no change
I have tried all of its gates:
Pin 1 IN : Pin 2 OUT
Pin 3 IN : Pin 4 OUT
Pin 5 IN : Pin 6 OUT
and so on...
When I tie any input LOW (to GND) its corresponding output goes HIGH and vice versa.
But when I drive it from the PS2505 via a 120VAC switch it doesn't work
I have attached the relavent datasheets and a schematic of the section
I'm not sure your hookup to the PS2505 will work. Try grounding the emitter, put a 4.7K resistor pullup on the collector and feed the 7414 from the collector.
Based on what you have both suggested I have drawn a new schematic (see Schematic#1 attached), however if I am correct there is a voltage divider between the output of the PS2505 and the input of the 7414.
If that is the case, should I do something like schematic#2 attached ?
You shouldn't even remotely think of using TTL these days, A 74HC14 (CMOS) schmitt-trigger will
have the voltage thresholds much more sensibly nearer to mid-rail, and present no load on the input circuit.
For a regular TTL chip you need ~470 to GND on an input to guarantee a low.
On LS TTL 1.2K will work.
You shouldn't even remotely think of using TTL these days, A 74HC14 (CMOS) schmitt-trigger will
have the voltage thresholds much more sensibly nearer to mid-rail, and present no load on the input circuit.
The IC that Rosscopicoptrain provided a link to in his original post was in fact a CMOS version, 74HC7014.
Referring to it by the generic name 7414 might have caused some confusion.
It looks to me as though the circuit in question is meant to be a zero voltage detector for use in a phase controlled power controller.
If that is the case, (and as far as I can see that has not been mentioned yet in this topic), then I think that there is a major problem with the circuit.
Using a capacitor and resistor to drop the voltage to the LEDs is going to give a phase change to the current through the LEDs. (I know you have done it to reduce power dissipation in the circuit as a whole).
Using an on-line calculator, it looks to me as though there is a 72° phase difference between the current through the LEDs and the main current. As far as I can see, there will always be this 72° offset.
The calculator also suggested an impedance of around 8.3kΩ, I'll discus the implications of this in my next post.
JohnLincoln:
The IC that Rosscopicoptrain provided a link to in his original post was in fact a CMOS version, 74HC7014.
Referring to it by the generic name 7414 might have caused some confusion.
Yes, wrong part numbers always adds to confusion I find.
JohnLincoln:
If that is the case, (and as far as I can see that has not been mentioned yet in this topic), then I think that there is a major problem with the circuit.
Using a capacitor and resistor to drop the voltage to the LEDs is going to give a phase change to the current through the LEDs. (I know you have done it to reduce power dissipation in the circuit as a whole).
That part is a circuit I found as I am not entirely familiar with using reactance when designing circuits.
Another question, I am trying to do hardware debouncing between the PS2505 and the 74HC7414. However all of the debouncing circuits I have found so far have a 10K pullup and a 0.1uF to ground.
Since I am using a 470 to ground, should I be putting the capacitor between the PS2505 output and VCC ?
