Hi All,
I am very new to this with very little knowledge of electronic components!
I've attempted to create the 'Original Two-wire Game Show Timer' In this link found from another thread.
http://www.techlib.com/electronics/games.html
I've built it without the buzzer, buzzer battery and the 12v relay 200 ohm coil from the base unit... basically i built it like the diagram attached...

Here are some problems that i've encountered:
1. Lights flash when turned on.
2. lights do NOT stay on after releasing a contestant's station switch.
3. Some contestants are cheating! two of the 4 contestant stations i've built tend to over ride other stations.

It took me all day to build this with no success... any ideas? (I've also attached a typ. contestant station wiring)

Thank you.

 

In your hand-drawn diagram you've indicated a capacitor in parallel with the light bulb, but I believe it should be a zener diode if you are following the circuit you linked. The photo appears to show a zener.

Oh wait, your hand-drawn is the base station? So you want have 2 bulbs that light up when a contestant's button is pressed, one at the base and one at the contestant? As shown you'll have a substantial (12V?) voltage drop across that lightbulb.

 

I traced out your plywood creation, and the circuit looks nothing like anything on the page you linked. I believe you have your SCR gate tied directly to ground, so that's prevented from coming on, and probably why the light doesn't latch on. You've put a 1Kohm resistor, 220ohm resistor, and 15V zener in series with your contestant switch to ground; I see non of these components in the link and can't figure why you'd add them. What's the purpose of the capacitor?

That's the differences I see between your circuit and the one in the link, but I'm not sure even if you built it per the given schematic that it would perform the way you want. I see no provision in the circuit to allow only the first contestant who pushes the button to light his/her light. It seems all 3 (or however many) could light their lights at the same time.

 

You need to look down to the right circuit:

 

You need to look down to the right circuit:

DOH! thanks. But I still think he's got the gate connected to ground.

 

check out the CD106 datasheet. It shows the metal tab being the front of the chip, not the back. So gate is on the right and cathode is on the left, as shown in the PDF pic. I think those need to be swapped.

 

check out the CD106 datasheet. It shows the metal tab being the front of the chip, not the back. So gate is on the right and cathode is on the left, as shown in the PDF pic. I think those need to be swapped.

Thank guys for the reply!
This is the data sheet i was given by the store when i purchased the parts..
Is that still wrong??

 

check out the CD106 datasheet. It shows the metal tab being the front of the chip, not the back. So gate is on the right and cathode is on the left, as shown in the PDF pic. I think those need to be swapped.

Swapping done...
Non of the lights turn on at all now!
Might be worth looking at the base unit modification (check the diagram in the source link vs. the modified diagram that i did) does that look like it could be the problem?
Also, any ideas on why the lights flash instead of light up continuously!?

 

...
It shows the metal tab being the front of the chip, not the back. So gate is on the right and cathode is on the left, as shown in the PDF pic. I think those need to be swapped.

Sorry, but flat pack SCRs are almost always KAG looking from the front (where the part number is printed).

 

Sorry, but flat pack SCRs are almost always KAG looking from the front (where the part number is printed).

does that mean i got them correct way around?

 

Probably the first time.

It's a poor circuit, it relies on properties of the main PSU source vs the zener voltages, and the main PSU source must drop it's voltage after one station is activated. When the main PSU source voltage has dropped, the zener in each station stops it being activated.

I would prefer a much more direct "lock out" of stations that does not rely on specific behaviour of the PSU source.

For instance, you could have each station as one button, one SCR and one light bulb.

So each station can lock ON it's own light bulb. The button (and gate) can be driven from a shared bus wire, that has a resistor to +12v.

Then for a "lock out" you put one diode on each station, from SCR anode to the shared bus wire. So, after any station has latched on, its diode will drag that shared bus wire down to 1 or 2 volts, and after that occurs no other station can have enough gate volts to turn on.

That gives you the same basic functionality where the first station to be gated "locks out" all the others, AND still gives you the option to add as many stations as you like. Each station requires two wires for +12v/gnd, and a third wire for the shared bus wire.

 

Ok, i've opted to go back to the easy simple diagram (though i have doubled the voltage and the numbers for everything!). but there is trouble!
The system works but sometimes multiple contestants' lights will light up (at half power, very dim), and that is a problem because the whole idea of it is that when one contestant hits the button first his and only his light bulb will light up...
so here is what i have...
Attached:
-original diagram-before modification
-New Base unit
-New Contestants unit

 

Still a bad circuit. The one I suggested in the last post needs a few extra diodes but is not that much more complex, and should be very reliable.