Hi, this is my first successful post. I recently started a personal electronic project that began with a great deal of confidence but I have literally hit a brick wall, although the project is half completed.

Let me begin by bringing you up to date on my project. My plan was to simulate a series of the normal logic gates on a solid piece of plastic (8 1/2 in by 11 in). Each row (8 1/2 in long) would simulate one logic gate. Also, each of the four rows that I have completed now contain the following; 1) one sub-mini on-off SPST toggle switch so each row can be operated independently, 2) two momentary push button switches, 3) a 270 Ω 1/4 watt resistor and 4) an LED. I drilled the holes wired and soldered all the connections. So, the four completed rows are AND, OR, NAND and NOR gates. The power is supplied by a 9 volt battery. So, for example, to test the AND gate I would flip the toggle switch on, and not pressing any momentary push buttons the LED would not illuminate, or pressing either momentary push button would also not illuminate the LED, but pressing both of them at the same time would illuminate the LED. The AND and OR gates use N. O. momentary push button switches and the NAND and NOR use N. C. switches. To this point everything works great!

I have attempted (without success) to simulate XOR and XNOR gates. SPST switches, would not work. I don't think I have enough space for DPDT switches and its wiring even if they would work. So, I looked into CD4070 and CD4077 ICs (2-Input Quad XOR and XNOR). I have studied their data sheets and have a very basic understanding of them, but no experience in working with CMOS or TTL. Is it possible to use 1/4 of the above quad ic or do all 4 have to be used? If all 4 are used, would the output be altered to produce something other than XOR or XNOR? My electronic experience is limited and I normally experiment until I find success. In this case I don't know where to start or how to use this type of IC. I have used the 555 IC, transistors, capacitors and a few other components with varying degrees of success. Could you offer some direction or suggestions on how to complete this project? I won't give up. I just need some professional advice. Thanks

 

I'm having trouble understanding how you can have room for two SPST switches and an IC, but not for two SPDT's (why would you need DPDT?).

 

You can simulate an XOR circuit with two SPCO (SPDT) switches;
connect input to one common, take output from the other common, then connect NO on the first to NC on the second, & NC first to NO second.

If either one is on & the other off, you get a circuit through: XOR function.

(It's one was of doing the standard domestic 'two way lightswitch' setup).

 

Thanks for the reply. The acronym DPST just sounded like a large switch. After posting my message I looked at a Jameco catalog and noticed mini DPDT were really very small. My impression of the acronym led me to believe it was large. My knowledge in electrical/electronics is limited, but I am learning a little at a time.

Thanks again for the reply.

 

I am new to this site and I hope this message is reaching Ron H. My assumption of the acronym DPDT sounded like it was a large switch. After posting my message I looked in a Jameco catalog and noticed there are mini DPDT switches which are very small. As for thinking I needed a DPDT switch, was mainly due to wiring several different ways a couple of SPST switches in an attempt to to make a XOR gate. I finally realized this would not work. I know just about enough to get myself in real trouble.

Thanks for the reply.

 

I may have sent you the wrong message. If I did, I apologize. As you probably can figure out I don't have a great deal of knowledge in what I attempting. Thank you for reply concerning the use of SPDT switches. I will certainly give it try. Again thanks for the reply.