I have the circuit is working as needed. Now I need to move it from the breadboard to a circuit board. I think this could be worse than designing and testing the circuit.

I find that printing a copy of the schematic and using a highlighter on each part and each wire as I connect it minimizes my errors. I use the same procedure to confirm my schematic matches my breadboard.

 

Thanks for the suggestion, I will do this when building my first circuit board. I am afraid to tear down the bread board until I get at least one circuit board built and operational. I figure this will be my final confirmation that my schematic is indeed correct.

 

Looks good. I like the fact that eye 1 controls the reset of the timer and eye 2 triggers it. Nice.

A few comments:

You can connect pin 8 directly to GND - no need for the 10kΩ resistor.

Be sure to add a 1uF electrolytic and a 0.1uF ceramic capacitor as close to Vcc and GND of the 556 as reasonably possible to help eliminate noise on the circuit.

Do the same for the 4025 and NOT gate ICs using just a 0.1uF ceramic for each.

When drawing schematic, there are generally two ways to show connections at intersections - with dots or with arcs. Arcs are used to show two crossing paths are not connected. When this method is used, dots are not shown - it is assumed any intersections without arcs are connected. Dots work in the opposite way - if two paths intersect and there is a dot, they are connected. If no dot is present, then they are not connected.

Dots are generally the preferred method and are, at least in my opinion, easier to read than arcs. You never use arcs and dots together since there is no need and it would add confusion.

Overall though, the schematic is well drawn and easy to read. Great job!

One question though - are you planning to have the skip timer on all the time? If not, how do you wish to control it - via a signal from somewhere or a simple toggle button flipped by the operator? If the latter, I'd suggest a SPDT switch connected to pin 4 of the CD4025. One side would be fed from pin 10 of the NOT gate IC, the other would be connected directly to GND. In this way you can ignore the skip timer if desired and maintain normal operation of your circuit.

 

elec_mech, thanks for the feed back. Your idea to turn off skip pattern with toggle switch attached to pin 4 of the CD4025 is eactly what I was inrending to do. I also need to interface another panel switch that allows the user to turn off the entire circuit or switch the circuit into test mode. Where test mode would simulate the action of a box going past the eyes only using a toggle switch.

The Auto/Off/Test switch I was planning on doing the follwoing:

Off: I was going to open or switch high thru a resistor, pin 8 on the CD4025 .

Auto mode: I was going to place pin 8 on CD4025 to normal position

Test mode: I was going to use a toggle switch to drive pins 1 & 2 low. I have to test this to see how the timing of the entire circuit will work since the toggle switch will drive both inputs low at the same time instead of one then the other.

Thanks again for all your input and questions.

Dave

 

Off: I was going to open or switch high thru a resistor, pin 8 on the CD4025 .

If you use a SPDT switch, you can connect the common to pin 8, one side to GND, and the other to Vcc. In this way you don't need a resistor. A SPDT will break-before-make and doesn't require a resistor, so that would be my vote.

If for some reason you're stuck with a SPST switch, you can connect pin 8 to a pull-down resistor as you did in your schematic then connect one end of the switch to pin 8 and the other directly to Vcc.

Test mode: I was going to use a toggle switch to drive pins 1 & 2 low. I have to test this to see how the timing of the entire circuit will work since the toggle switch will drive both inputs low at the same time instead of one then the other.

As you mentioned, I'm not sure this would allow the timer to come on properly since both reset and trigger will occur simulateously.

If makes sense, I'd suggest two switches to simulate the two eyes. Again, a SPDT would be nice, but a SPST could work. Only caveat here is switch bounce which may result in strange operation, but you could add a resistor and capacitor to help with that.

Alternately, you could make a test circuit that simulates the operation of the eyes detecting a passing object.