How would I make a circuit for 3 players for Jeopardy? Here is the outline:

- 3 push buttons for players
- 1 "host" which enables/disables lights (basically clear)
- Each contestant has 1 led
- After 1st contestant pushes button, light is on and other 2 are "locked out"
- Led remains on for 5 seconds then auto-clears or "host" clears and other contestants re-enabled

I would prefer using 74XX series but anything would be helpful!!

 

Try searching for "game show circuit" or "quiz show circuit".

 

I have. I've tried for over 2 hours simulating on multisim but they don't fit the requirements and chips I have. (I'm limited to 74XX chips because that's the only ones my school has.)

 

Look in the Completed Projects section, and my game show circuit is there. It meets most of your requirements and could easily be added to for the rest.

I used CMOS 4000 series, but the same chips are available in TTL 7400 series
7408 = 4081
7421 = 4082
7474 = 4013

The output of the 4 input AND gate (used to lock out further input) can also be used to trigger a timer to self reset.

Just don't use the 4th input for only three players.

 

I'm thinking of a two ic solution.

Possibly a 7410 triple 3 input nand and a 7404 hex inverter.

One input of each nand pulled high from respective switches. (activate)

Output of each nand to an input of the remaining nands. (inhibit)
Outputs buffered thru remaining inverters for LED. (output)
Output of each nand thru inverter and diode to latch it's own switch input high. (latch)

Cycle power. (reset)
Or use two input nand gates in lieu of inverters, for latching and reset.

ps.
Don't mean to distract from a working plan.
Just posted my thoughts on a simple approach. (that in all probability won't pan out)

 

Here is one that I simulated and it worked.

Looks like a hybrid of djsfantasi and inwo's idea.

Do you know how to simplify the circuit further to reduce the amount of chips used?
The answer is in the schematic.

Allen

p.s. If you do a google search under images, there are plenty of schematics of this nature. My schematic was a slight modification of one of the circuits I found there...

 

You can do it with a very simple circuit; one SCR per contestant.

 

Yes, you're right...

But the OP specifically said

I would prefer using 74XX series but anything would be helpful!!

SCR would be much simpler.

Allen

 

The output of the 4 input AND gate (used to lock out further input) can also be used to trigger a timer to self reset.

How would I use the 4 input AND to trigger the self reset?

Here is one that I simulated and it worked.

Looks like a hybrid of djsfantasi and inwo's idea.

Do you know how to simplify the circuit further to reduce the amount of chips used?
The answer is in the schematic.

Allen

p.s. If you do a google search under images, there are plenty of schematics of this nature. My schematic was a slight modification of one of the circuits I found there...

Wouldn't a nand followed by an inverter simply be an and?

 

Below is the simplest circuit I could come up with using 7400 logic. The circuit uses 3 JK Flip-Flips (2 packages) and one 3-input NOR gate. The FF changes state with the first switch to be pressed (connected to ground) which causes the NOR gate to change all J inputs to low, preventing further operation of the FF's. (Switch 1 is shown depressed, lighting LED 1). Switch R resets the FF's for the next round.

If the switches are SPST then you can use a 10kΩ pull-up to 5V on each switch output to maintain the high state when the switch is not pressed. (The FF's output changes state when the clock or reset goes low.)

The FF's can sink up to 16mA on their outputs to directly drive the LEDs.

 

Here's the update: I got the 3 buttons to work and fit into my quota. What I need is the last quota which is for the LED to remain on for 5 seconds then auto-reset & re-enable others. Would I use a monostable 555 to achieve this?

 

Yes,
Or,

How about 3 555s in lieu of the flip flops?

 

Here's the update: I got the 3 buttons to work and fit into my quota. What I need is the last quota which is for the LED to remain on for 5 seconds then auto-reset & re-enable others. Would I use a monostable 555 to achieve this?

Yes you could use a 555 for the delay but you may need to use two 555's (or one dual 556). The first generates a one-shot 5 second delay and the second triggers at the end of the delay to generate a short one-shot pulse to reset the circuit.

 

Here's the idea for triple 3 input nand and 3 555s.

I don't know if diodes and caps are allowed.

Manual reset from 555 reset pin.

555s replace inverter, output buffer, and FF. Also takes care of time delay and reset.

Pull up/down shown edit...............................

http://www.digikey.com/schemeit/#tkp

 

This circuit checks the 5 second quota off, but it also makes the moderator switch useless and fails to lock out the other LEDs so all of them can be on at the same time.

Here's the idea for triple 3 input nand and 3 555s.

I don't know if diodes and caps are allowed.

Manual reset from 555 reset pin.

We don't have any 3 input NANDs. Quite frustrated about my schools low budget.

 

Below is my circuit with two 555's added to generate a reset after about 5 seconds. The first 555 generates the 5s delay and the second 555 generates a short pulse to reset the FF's.

Edit: Do you have 3 input OR or NOR gates?

 

Below is my circuit with two 555's added to generate a reset after about 5 seconds. The first 555 generates the 5s delay and the second 555 generates a short pulse to reset the FF's.

Edit: Do you have 3 input OR or NOR gates?

View attachment 68494

I only have 2 input OR and NOR gates, but I can create 3 input from them. I'm not sure how to create a 3 input NOR from 2 input NOR, but know how to from an OR. Also, I have 7476 instead of 7473. Only difference is that 7476 has a preset. Would I leave that grounded or what?

 

There should be an equivalent circuit for my 3 input nand.

Is this it.

I believe it's the same with middle nand inputs tied together.

 

I only have 2 input OR and NOR gates, but I can create 3 input from them. I'm not sure how to create a 3 input NOR from 2 input NOR, but know how to from an OR.

You can connect the outputs of two 2-input NOR gates to two respective inverters (giving the OR function) and then the inverters to a third 2-input NOR to give a 4-input NOR gate.

 

You can connect the outputs of two 2-input NOR gates to two respective inverters (giving the OR function) and then the inverters to a third 2-input NOR to give a 4-input NOR gate.

I don't know why, but your schematic doesn't seem to work for me. I don't know if it's the program I use (multisim) or what. I used the same chips and numbers but still no result.