My sister and wife are in education, and the kids play a "Jeopardy" like game in the classroom. I wanted to make a circuit for them to use. After seeing several threads regarding game show circuits and attempting (unsuccessfully) to simulate many of them. I decided to attempt my own.

My circuit is for four players, and once anyone had pressed his/her button, their LED will illuminate and the circuit will lockout from any other inputs.

I used a 4013 D-type flip flop with the clock connected to a pushbutton input (more on this in the next paragraph) They clock on the rising edge. The D input is tied high, so that starting from a reset state (Q is low; Q' is high), the Q output will go high on a rising edge. The Reset inputs are held low with a pulldown resistor, and will reset when the input is brought high.

Locking out other players when one button is pressed is done by first sending the clock input through an dual input AND gate. The second input of this gate for each player is tied to the output of a quad input AND gate, whose inputs are driven through Q' from each flip flop. Thus, when one player buzzes in, his Q' will go low, all the AND gates will prevent input to any clock, thus effectively locking everyone from changing the state.

The parts I used are listed below, including part numbers from Digikey:

Qty Digikey # Description
9 CF18JT4K70CT-ND RES 4.7K OHM 1/8W 5% CF AXIAL
1 67-1153-ND LED 3MM YELLOW DIFF PANEL MOUNT
2 A31112-ND CONN HEADER VERT 2POS .100 TIN
2 S390QCT-ND RES 390 OHM 1/4W 5% CF MINI
1 708-1403-ND HOLDER BATTERY 1 CELL 9V
4 8714K-ND STDOFF HEX M/F 4-40 .250"L ALUM
1 377-1217-ND BOX ABS 4.61X4.61X2.36" BLK
4 CP-3502MJ-ND CONN AUDIO JACK 3.5MM MONO
5 450-1110-ND NO PUSHBUTTONS
1 on hand SPST SWITCH
4 751-1116-ND LED 5MM GREEN 15MCD GAP ON GAP
4 A100205-ND CONN IC SOCKET VERT 14POS TIN
1 568-1702-5-ND IC GATE AND QUAD 2INPUT 14DIP (4081)
1 568-1703-5-ND IC GATE AND DUAL 4INPUT 14DIP (4082)
2 296-2033-5-ND IC DUAL D-TYPE FLIP-FLOP 14-DIP (4013)

Attachments are included to show the schematics. They were created using ExpressSCH.

The board layout for creating the PCB is below. There is also attached a picture of an improved layout I developed.

Note that in version 2, I used a 4k7 resistor SIP instead on discrete components, as suggested by kubeek.

Also attached are the schematics for the complete circuit. The original ExpressSCH and ExpressPCB files are included in the zip file.

 

Here is a schematic!

 

...and here is a printed circuit board layout!

 

Can anyone comment whether they see any problems either in the schematic or PCB layout, pre-investment on my part? I know the circuit does not show the power filter cap (47μF), nor the decoupling caps (0.1μF), but I just told you

Besides, they are on the PCB. Also omitted is the fact that the power supply is a 9VDC battery.

Thanks.

 

You're going to make 2 pcb out of your design - one for logic and one for LED. Why not make the connections of the LED PCB close to each other? The 5 connections on the LED pcb are scattered and makes the connections look messy. If possible I would put a 5 pin connector on it.

Is there a single sided PCB layout? It would more appealing for others to duplicate if it were made using single sided PCB.

Thanks.

Allen

 

I wanted to separate the LEDs to make them easier to identify as to which one is lit and to have a wide space to label them on the case. The separate board will be mounted to the case and connected to the logic board via a header. Also, I could only squeeze .3" on the board (manufacturing limitation; see next paragraph)

I felt there were too many jumpers required for single-sided board, particularly around the 4081 and the outputs of the 4013s. Besides, I use ExpressPCB to make my boards and a double-sided board is easy. I use their mini-board service (three 3.8" x 2.5" boards for $75 + s&h)

But your points are well taken. Thanks for responding.

 

I think I misunderstood your comment. I have redesigned the PCB LED Display portion, so that pads for the the wires to the header socket are contiguous. I am using modified servo cables, connecting to a six pin header for both the LED display (lower right of the logic portion) and the pushbutton input (left side of the logic portion).

The LED Display will be mounted to the case with 1/4" standoffs. The 9v battery, power switch and reset pushbutton will be connected via header pins to the case as well, so everything can be disconnected for swap out, debugging or during construction.

 

There ended up being additional discussion about this circuit in the following thread:
http://forum.allaboutcircuits.com/showthread.php?t=82979
I am including the cross-reference here for anyone interested.

I am also attaching a more complete schematic, generated with ExpressSCH. Since I am a basic hobbyist, this program and its sibling, ExpressPCB, are tools I use all the time.

I have all the components (BoM attached, too) and the PCB is on order! I've been preparing the project box for mounting the external components. The PCB should arrive next week, and then the soldering begins in earnest.

dj

 

There is a nice circuit on Electronics Club website that uses 555 and does a similar thing.

 

To go off in a totally different direction...dirt simple...http://www.techlib.com/electronics/games.html
I've built several versions of the circuits shown.

Ken

 

@KMoffett,

I've also seen the original circuit, based on SCRs. Interestingly, the digital circuit shown in your link is similar to my circuit.

I redesigned my PCB (but went with the original design for my prototype.) It looks better. I am using a SIP resistor network as suggested by kubeek. Also, by chaging some pin assignments, it became easier to route the signals, so that they run either horizontally or vertically. I've attached the picture here...

 

Finally got this working. A couple of obvious notes!

• Make sure that the correct chips are inserted into each socket. You can let magic smoke escape otherwise.
• Carefully insert the chips into their sockets. You can physically destroy a chip otherwise.
• Be careful when ordering components. An 820Ω resistor is not an 820kΩ resistor.

When inserting the pushbuttons, if power is applied, the LED corresponding to the first one inserted will go on. This can be used during testing. Insert one pushbutton and verify that its LED illuminates. Then move the pushbutton. The display should not change. Reset the circuit and press the pushbutton. Its corresponding LED should light. Repeat...

When first powering up, a random LED may be lit. It is always recommended to reset the circuit upon first powering on.

I found it incredible how fast the circuit responds.

 

As you show it, the four switches have to be wired together into a single wire harness because of the common Vcc connection. I recommend expanding the Vcc connections at the switch input connector to one Vcc per input. This makes each switch interface the same: switch, two wires, two-wire connector.

Also, the 4082 can be replaced with four diodes and a resistor. Going further down that road, the two 4013's can be replaced by two 4093's since you really don't need a clocked FF. If you keep going, the 4081 can turn into a 4093, and now all chips are the same. (I have a thing about inventory reduction.)

ak

 

As you show it, the four switches have to be wired together into a single wire harness because of the common Vcc connection. I recommend expanding the Vcc connections at the switch input connector to one Vcc per input. This makes each switch interface the same: switch, two wires, two-wire connector.

Also, the 4082 can be replaced with four diodes and a resistor. Going further down that road, the two 4013's can be replaced by two 4093's since you really don't need a clocked FF. If you keep going, the 4081 can turn into a 4093, and now all chips are the same. (I have a thing about inventory reduction.)

ak

The harness shares the Vcc connection; the switches plug into jacks, providing two wires to the switch. The wiring of the jacks split the common Vcc connection to one Vcc per input.

I understood how to make the circuit latch with the 4013 and not so much with the 4093 latching circuit (RS FF). Even if someone released their button after pressing it, I wanted the circuit to remember the first press. My ignorance.

I had considered the diode-OR, but wanted to keep the circuit inventory consistens; i.e., all 4000 series logic.

 

djsfantasi,

In order for your post to be a nice Completed Project, it would be nice if you summed up your project description and most recent files in the first post.

Include:
A description,
A schematic
A digital file for the board description
A Bill of Materials

I'll duplicate the first post, so that you can edit it with the necessary components.

 

After seeing several threads regarding game show circuits and attempting (unsuccessfully) to simulate many of them. I decided to attempt my own.
My circuit is for four players, and once anyone had pressed his/her button, their LED will illuminate and the circuit will lockout from any changes.

I used a D-type flip flop with the clock connected to a pushbutton input (more on this in the next paragraph) They clock on the rising edge. The D input is tied high, so that starting from a reset state (Q is low; Q' is high), the Q output will go high on a rising edge. The Reset inputs are held low with a pulldown resistor, and will reset when the input is brought high.

Locking out other players when one button is pressed is done by first sending the clock input through an dual input AND gate. The second input of this gate for each player is tied to the output of a quad input AND gate, whose inputs are driven through Q' from each flip flop. Thus, when one player buzzes in, his Q' will go low, all the AND gates will prevent input to any clock, thus effectively locking everyone from changing the state.

Perhaps a picture or two will help.

 

djsfantasi,

In order for your post to be a nice Completed Project, it would be nice if you summed up your project description and most recent files in the first post.

Include:
A description,
A schematic
A digital file for the board description
A Bill of Materials

I'll duplicate the first post, so that you can edit it with the necessary components.

Please review now? I think I have everything

 

I added the entry to the Completed Projects Collection.

When I mentioned digital project files, I meant the ExpressPCB files, so that one can easily print them for themselves, without having to design the board from scratch.

Can you add these too? If the Attachment Manager doesn't allow the extension, put them in a zip file.

 

By the way, I did attach the ExpressSCH and ExpressPCB files.

I did run into another problem. The small wires from the servo extension cables that were used to connect the input push buttons and the output LEDs broke off at their soldered ends. After repairing the damage, I strengthened the joints with a covering of hot glue. This took the strain off from the PCB / jack terminal to wire connection.

Thanks for the JK flip flop suggestion. I'll look into that the next time, after I use up the PCBs I've had made.