# Switch module test circuit design

I am doing a project to make a test box that would to test the switch module in the photo below. Please see circuit diagram below for inside of the switch. Please note this switch is not an ordinary switch has it resistors inside which is more complex.

So far I have designed the test box circuit using various way and methods I have used 555 timer circuit, Transistor and finally using NAND logic gate. The best option was the last one using NAND Logic gate as it worked the way I wanted by using 10k resistor and 3 LEDs using the truth table however due to my switch circuit on the inside this would not work.

A B  Output
0 0   1
0 1   1
1 0   1
1 1   0


This NAND gate logic worked on circuit simulation tool after using two ordinary switches. However when I try to integrate my tester box switch to the switch I have noticed my switch is much more complex has its got a circuit inside with resistors which I couldn't integrate the two circuits.

The only other idea I have is to do this using Arduino and program it maybe. Can anyone tell me ways to do this, as I have running out of ideas now.

Reference A

Reference B

Reference C

Reference D

PS:

@jonk Apologies for misclarification yes the buttons are momentary and no its not latching magnet motion. Also its not random switch its got circuit inside which indicated above, my goal is just to test the switch if there are connected or not and their state by showing me LEDs to indicate that. ''wanting to push those buttons to verify they work correctly?'' Yes I want to verify if they work and connected

1. Is someone is going to connect the switch module, press the buttons in all four NAND combinations and watch the LEDs? - Yes the switch is going to be connected with the NAND circuit and watch the LEDs if they are connected and works.
2. Does the test circuit need to confirm the presence of the four resistors? - yes the resistor circuit should confirm the four resistors including the switches, In fact it should configure the switch circuit diagram and it should work by simulating and integrating with NAND gate (tester box circuit).
3. Does the test circuit need to check the values of the four resistors? - Yes it should.
4. Your simulation doesn't show the four internal resistors. Why not? - The four resistor from my switch circuit diagram has not been simulated yet - the simulation circuit above is my tester box circuit and however the 2nd image is the switch circuit from the supplier data sheet .
5. Why do you require a NAND? - This NAND logic works well to what output I want to achieve, I want the ouput to be on what input is inserted. If any other circuit suggestion do please let me know.

Sorry I think I have confused you and you have misunderstood my question. Now I have reference each image clearly i.e (References A-C). So the switch unit in Ref A is what I am trying to test, the switch unit has got a on-board installed circuit see Ref B, Also please note that REF B circuit diagram is already been given by the supplier. In other words Ref A&B are equivalent. As you can see from the circuit diagram REF B that which doesn't not have or contain any a power supply at all. So Ref C is just an draft circuit that I was hoping it would work and I could able to test switch unit in Reference A;- by connecting REf B to the REf C (the circuit I have created ) to test the switch unit REF A. So just to sum up and answer your question ''What two circuits? '' One circuit is Ref A and other REF C. Also this Ref A switch unit is much more complex to test since its got 4 resistors inside and 3 pins see image and its not just an ordinary simple switch(Reference D)

• I don't think I fully apprehend your goals. I don't see a datasheet listed and it's not clear to me if those buttons are momentary, or not. (Reeds often are. But it is possible to mechanically arrange latching magnet motion, too. So I don't know.) Are you taking random switches and just "testing their state?" (Which would imply they are mechanically latching to me.) Or are you wanting to push those buttons to verify they work correctly? Or? It's possible I'm not even close, too. So could you expand a little on the goals? – jonk Jan 8 at 15:14
• I have fixed the formatting and some other details in your question. Please edit your question to explain: (1) Is someone is going to connect the switch module, press the buttons in all four NAND combinations and watch the LEDs? (2) Does the test circuit need to confirm the presence of the four resistors? (3) Does the test circuit need to check the values of the four resistors? (4) Your simulation doesn't show the four internal resistors. Why not? (5) Why do you require a NAND? Why can't you watch the output of pins 1 and 2? Put all the information into your question and not in the comments. – Transistor Jan 8 at 19:20
• @jonk Apologies for misclarification yes the buttons are momentary and no its not latching magnet motion. Also its not random switch its got circuit inside which indicated above, my goal is just to test the switch if there are connected or not and their state by showing me LEDs to indicate that. ''wanting to push those buttons to verify they work correctly?'' Yes I want to verify if they work and connected. – M.salimy Jan 9 at 8:16
• @(1)Transistor Is someone is going to connect the switch module, press the buttons in all four NAND combinations and watch the LEDs? - Yes the switch is going to be connected with the NAND circuit and watch the LEDs if they are connected and works. (2) Does the test circuit need to confirm the presence of the four resistors? - yes the resistor circuit should confirm the four resistors including the switches, In fact it should configure the switch circuit diagram and it should work by simulating and integrating with NAND gate (tester box circuit). Please see the rest answers on the question – M.salimy Jan 9 at 9:16

simulate this circuit – Schematic created using CircuitLab

Figure 1. A simple test fixture.

This simple test fixture might suffice.

Switch testing:

• With SW1 off about 2.5 mA will flow through D1 lighting it dimly.
• With SW1 on about 13 mA will flow through D1 lighting it brightly.
• With SW2 off about 2.5 mA will flow through D2 lighting it dimly.
• With SW2 on about 10 mA will flow through D2 lighting it brightly.

Resistor testing:

• If R1 or R3 is missing the dim test will fail.
• If R2 or R4 is missing the respective LED will never light.
• Thank you so much for your circuit really helpful, however I am not so sure how you would connect the above simple circuit you created into the test box circuit i.e the NAND gate circuit that i have created with 3 LED outputs to verify if each switch's are connected and the state LED output I am after is when its not connected the LED is OFF and When its connected the LED is ON . IF you think that circuit above (Nand gate) will not work with the Figure (Figure 1. A simple test fixture) then please provide an alterntive circuit so it works out when the two circuits are connected to my testbox – M.salimy Jan 9 at 7:45
• Forget the NAND circuit. Just plug the switch unit into the circuit above and watch the two LEDs as you press the buttons. If you have some other requirement then it is not clear. "... when the two circuits are connected to my testbox." What two circuits? There is only one circuit in each switch assembly. – Transistor Jan 9 at 13:49
• Do you have email I can send you documents and circuit diagram and clarify the question clearly as I have limited word here – M.salimy Jan 9 at 14:45
• Certainly not. All discussion should be done on EE.SE. I'm not aware of any limit to the text you can add to your question. You are limited to the number of inline images until you get enough reputation. If you upload them someone will inline them for you. – Transistor Jan 9 at 17:07
• Sorry I think I have confused your misunderstood my question. So now I have reference each image clearly i.e (References A-C). So the switch unit in Ref A is what I am trying to test, the switch unit has got a on-board installed circuit see Ref B, in other words they are Ref A&B are equivalent. As you can see from the circuit diagram REF B that which doesn't not have or contain any a power supply at all. Also please note that REF B circuit diagram is already been given by the supplier. *See above in details – M.salimy Jan 10 at 7:36