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Circuits Testing/Measuring Game Show Indicator Lights (Who's First)
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Circuits Testing/Measuring Game Show Indicator Lights (Who's First)
Game Show Indicator Lights (Who's First)
The circuit above turns on a light corresponding to the first of several buttons pressed in a "Who's First" game. Three stages are shown but the circuit can be extended to include any number of buttons and lamps.
Three SCRs (silicon controlled rectifiers) are connected with a common cathode resistor (50 ohm) so that when any SCR conducts, the voltage on the cathodes will rise about 7 volts above the voltage at the junction of the 51K and 1K ohm resistors and prevent triggering of a second SCR. When all lamps are off, and a button is pressed, the corresponding SCR is triggered due to the voltage at the divider junction being higher than the cathode. Once triggered, the SCR will remain conducting until current is interrupted by the reset switch. Or, you can just turn the power off and back on.
A 50 ohm, 5 watt resistor was selected to produce a 10 volt drop at 200 mA when a single 25 watt lamp comes on. Higher wattage lamps would require a lower value resistor, and visa versa. For example to use 60 watt lamps and maintain the 10 volt drop, the peak current would be 60/160 = 375 mA and the resistance would be E/I = 10/.375 or about 27 ohms at 3.75 watts. The SCRs are "Sensitive Gate' types which trigger on about 200 uA and the gate current is around 1.5 mA when the first button is pressed. The 1N914 diodes in series with the buttons gates are used to prevent a reverse voltage on the gate when a button is pressed after an SCR is conducting. The two resistors (1K and 50 ohm) will be fairly large in physical size (compared to a 1/4 watt size) and should be rated for 5 watts of power or more. Use caution and do not touch any components while the circuit is connected to the AC line.
Adding a Buzzer:
The relay shown in parallel with the 50 ohm cathode resistor can be used to momentarily power a buzzer with an external circuit through the contacts. The 1000 uF capacitor causes the relay to energize for about one second, longer times can be obtained with a larger capacitor.
Copyright 2007 Bill Bowden
Three SCRs (silicon controlled rectifiers) are connected with a common cathode resistor (50 ohm) so that when any SCR conducts, the voltage on the cathodes will rise about 7 volts above the voltage at the junction of the 51K and 1K ohm resistors and prevent triggering of a second SCR. When all lamps are off, and a button is pressed, the corresponding SCR is triggered due to the voltage at the divider junction being higher than the cathode. Once triggered, the SCR will remain conducting until current is interrupted by the reset switch. Or, you can just turn the power off and back on.
A 50 ohm, 5 watt resistor was selected to produce a 10 volt drop at 200 mA when a single 25 watt lamp comes on. Higher wattage lamps would require a lower value resistor, and visa versa. For example to use 60 watt lamps and maintain the 10 volt drop, the peak current would be 60/160 = 375 mA and the resistance would be E/I = 10/.375 or about 27 ohms at 3.75 watts. The SCRs are "Sensitive Gate' types which trigger on about 200 uA and the gate current is around 1.5 mA when the first button is pressed. The 1N914 diodes in series with the buttons gates are used to prevent a reverse voltage on the gate when a button is pressed after an SCR is conducting. The two resistors (1K and 50 ohm) will be fairly large in physical size (compared to a 1/4 watt size) and should be rated for 5 watts of power or more. Use caution and do not touch any components while the circuit is connected to the AC line.
Adding a Buzzer:
The relay shown in parallel with the 50 ohm cathode resistor can be used to momentarily power a buzzer with an external circuit through the contacts. The 1000 uF capacitor causes the relay to energize for about one second, longer times can be obtained with a larger capacitor.
Copyright 2007 Bill Bowden
Partlist
1x 4 Amp/400 Volt Bridge Rectifier
3x Silicon Controlled Rectifier (SCR)
3x 120 VAC/ 25 Watt incandescent lamp
1x 50-100 microfarad/ 200 volt capacitor
1x 1000 microfarad / 35 volt capacitor
2x 51 ohm resistor/ 5 or 10 Watt
3x Push Button Switch (normally open)
1x Push Button Switch (normally closed)
3x 2K resistor, 1/4 watt
4x 1N914 Diode
1x 51K resistor, 1 watt
1x 1K resistor, 1 watt
1x 2 Amp Fuse
1x Relay (SPDT) 9 Volt DC, 500 ohm coil
3x Silicon Controlled Rectifier (SCR)
3x 120 VAC/ 25 Watt incandescent lamp
1x 50-100 microfarad/ 200 volt capacitor
1x 1000 microfarad / 35 volt capacitor
2x 51 ohm resistor/ 5 or 10 Watt
3x Push Button Switch (normally open)
1x Push Button Switch (normally closed)
3x 2K resistor, 1/4 watt
4x 1N914 Diode
1x 51K resistor, 1 watt
1x 1K resistor, 1 watt
1x 2 Amp Fuse
1x Relay (SPDT) 9 Volt DC, 500 ohm coil
Files
Comments
Sep 13 2007 11:44
ashok
IN GAME SHOW INDICATOR CIRCUIT I WAS DOWNLOAD FROM YOUR WEBSITE. BUT I DONT KNOW HOW TO CONNECT THE RELAY INTO WHICH IS YOUR CIRCUIT ..PLEASE CLARIFY MY DOUBHTS AS SOON AS POSSIBLE..
Nov 25 2007 14:23
LZP8BW
Hi,
I’m going to build this circuit for my church and have a couple questions. First of all it seems like there are some discrepancies between the diagram and the parts list. I see 50 ohm/5-10 watt resistor and the 2 amp fuse in the parts list, but not on the diagram. Also, I see a 1K and 2-51/5 watt resistors on the diagram, but not in the parts list. Another discrepancy in the diagram is the 1000 microfarad/35 volt capacitor has a 25 volt designation in the diagram.
Regards,
Greg
I’m going to build this circuit for my church and have a couple questions. First of all it seems like there are some discrepancies between the diagram and the parts list. I see 50 ohm/5-10 watt resistor and the 2 amp fuse in the parts list, but not on the diagram. Also, I see a 1K and 2-51/5 watt resistors on the diagram, but not in the parts list. Another discrepancy in the diagram is the 1000 microfarad/35 volt capacitor has a 25 volt designation in the diagram.
Regards,
Greg
Nov 26 2007 21:58
Jospfh
Thanks for your remarks, I have updated the parts list regarding the resistors. The fuse should be mounted in one of the 120VAC lines.
As for the capacitor just take a 35V then you are always safe.
As for the capacitor just take a 35V then you are always safe.
Dec 28 2007 3:18
LZP8BW
Hi,
Thanks for the clarifications and updates. I have what I think is one last question regarding a change to modifying your design for each button to control a 60W string of tube lights. Your directions indicate a 27 ohm resistor at 3.75 watts will handle this configuration, but I can't find that configuration. Are there any other substitutes that will work?
Regards,
Greg
Thanks for the clarifications and updates. I have what I think is one last question regarding a change to modifying your design for each button to control a 60W string of tube lights. Your directions indicate a 27 ohm resistor at 3.75 watts will handle this configuration, but I can't find that configuration. Are there any other substitutes that will work?
Regards,
Greg
Dec 30 2007 22:37
Jospfh
First of all, I'm not the designer of this circuit. The designer is Bill Bowden.
But I think you can use any 27 ohm resistor which can at least dissipate 3.75 watts. so a 27 ohm resistor of 5 watts will do.
But I think you can use any 27 ohm resistor which can at least dissipate 3.75 watts. so a 27 ohm resistor of 5 watts will do.
