Need a quiz buzzer - Page 2 - Electronic Circuits Projects Diagrams Free

clifweb · 24th August 2006, 03:01 PM

I am having a look to try to solve it. One way that it works is by removing the wire that is after the 8 resistors and connecting it to the ground. But the reset switch didn't work than and neither the buzzer. i had to turn the simulation on and off in order to try another switch.

philba · 25th August 2006, 02:40 AM

PCB or circuit? I use eagle to create schematics and layout PCBs. I use switchercad/ltspice when I simulate - mostly analog or linear stuff. I never bother simulating digital as it's pretty straightforward. Generally, I just build the circuit and trace the signal when it doesn't work.

You should not be afraid to put a real circuit together. Use a solderless breadboard so you can make changes easily.

AllVol · 25th August 2006, 11:49 AM

Probably not a really big thing, but the transistor (T1 on the original) you are showing in your schematic (as I write this, with no changes) is an NPN. It should be a PNP. Look closely for any other errors like this.

AllVol

clifweb · 26th August 2006, 07:21 AM

Hope this simulation is easier to read. The 7 segment display works when a button is presses but the buzzer is not working and neither the reset switch. Please exam this so maybe I could get it to work.

AllVol · 26th August 2006, 01:35 PM

Thanks, clifweb, for cleaning up the schematic. Much better.

My quick reading of the logic involved leads me to believe the buzzer only works if two buttons are pressed at the same time, but I have no clue why the reset is not working. However, on just a sim, I doubt there is any way you would know unless you check the logic level at pin 1 of the 74LS147 to see if it changed. Probably that would not tell you much unless you reran the sim, and then you have simply gone back to the ready state.

I think you are ready to make a hard copy, and see what happens.

AllVol

milpitor · 26th August 2006, 06:00 PM

I think there are something wrong in your design:

- R10 should not be there.
- When pin#1 = 1, input is ignored.
- Why all input connect to GND?

AllVol · 26th August 2006, 06:51 PM

Okay, Clifweb, I have had time to give further study to your sim schematic. There are still some mistakes, but we are getting closer. Compare my corrections in the attachment below with your copy and I think you will see what I mean.

Yes, milpitor, R10 must be in the circuit, else when V+ is applied there would be a direct short. Pin 1 is active lo until a positive going pulse is applied. R10 is a pull-down resistor that keeps it low, but also prevents a short circuit.

Oops: I just saw another error. The connection between the ground side of C3 and the ground side of the buzzer should be eliminated.

AllVol

philba · 26th August 2006, 07:26 PM

doesn't the new wire from the bottom of C2 short it out?

also, the wires around /OE and LE look odd. not clear what's connect to what.

clifweb · 26th August 2006, 09:19 PM

Thanks very much the buzzer is now working. The only problem now is that I have to reset it manually. I was now thinking if there could be an addition part that could be later on added that when the buzzer is pressed a countdown will happen that could be preset but that it could be change with easily. Maybe having a + or – to increase or decrease the time. When the countdown hits 0 a sound will be heard to give the signal that the time is up. This unit will be separate of this circuit but has to be able to connect to it.

clifweb · 26th August 2006, 09:29 PM

This is the last simulation that I have run with I think everything is working but I have to reset each time. If there are some shot circuit please tell me. OE is connected to the ground. LE connected to pin 6 of the NAND gate.

AllVol · 27th August 2006, 04:06 AM

Clif,

Put R10 back into the circuit as it is supposed to be. With it not in line, you are shorting to ground when you press the reset button.

AllVol

AllVol · 27th August 2006, 04:18 AM

Hi, Phila,

Actually, according to the original schematic, his C2 should not even be there. But it's not really doing anything as it is.

AllVol

clifweb · 27th August 2006, 05:04 AM

When I put R10 back the circuit is not working. As I remove it the entire circuit will work. Instead of the 22k I made it 1K and it work. Do you think that that is ok.
C2 is present on the original schematic.

milpitor · 27th August 2006, 06:02 AM

try this, I think it's safer this way

clifweb · 1st September 2006, 10:12 AM

I have just built the buzzer on a breadboard to test it out before making it PCB. The circuit is working except that the 7 segment will only display the team number as long as that switch is pressed. Than it will be back to 0 after the switch is released. The buzzer is not working with the BC547 (As in the original schematic) the buzzer is not working at all but when instead of that I used the BC557 the buzzer kept on going the whole time. Can some one tell what he think is wrong.

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24th August 2006, 03:01 PM	(permalink)
clifweb	I am having a look to try to solve it. One way that it works is by removing the wire that is after the 8 resistors and connecting it to the ground. But the reset switch didn't work than and neither the buzzer. i had to turn the simulation on and off in order to try another switch. Last edited by clifweb; 24th August 2006 at 09:59 PM. Reason: spelling and better explantion

25th August 2006, 02:40 AM	(permalink)
philba	PCB or circuit? I use eagle to create schematics and layout PCBs. I use switchercad/ltspice when I simulate - mostly analog or linear stuff. I never bother simulating digital as it's pretty straightforward. Generally, I just build the circuit and trace the signal when it doesn't work. You should not be afraid to put a real circuit together. Use a solderless breadboard so you can make changes easily.

25th August 2006, 11:49 AM	(permalink)
AllVol	Probably not a really big thing, but the transistor (T1 on the original) you are showing in your schematic (as I write this, with no changes) is an NPN. It should be a PNP. Look closely for any other errors like this. AllVol __________________ All those who believe in psycho kinesis, raise my hand.

26th August 2006, 01:35 PM	(permalink)
AllVol	Thanks, clifweb, for cleaning up the schematic. Much better. My quick reading of the logic involved leads me to believe the buzzer only works if two buttons are pressed at the same time, but I have no clue why the reset is not working. However, on just a sim, I doubt there is any way you would know unless you check the logic level at pin 1 of the 74LS147 to see if it changed. Probably that would not tell you much unless you reran the sim, and then you have simply gone back to the ready state. I think you are ready to make a hard copy, and see what happens. AllVol __________________ All those who believe in psycho kinesis, raise my hand.

26th August 2006, 06:00 PM	(permalink)
milpitor	I think there are something wrong in your design: - R10 should not be there. - When pin#1 = 1, input is ignored. - Why all input connect to GND?

26th August 2006, 06:51 PM	(permalink)
AllVol	Okay, Clifweb, I have had time to give further study to your sim schematic. There are still some mistakes, but we are getting closer. Compare my corrections in the attachment below with your copy and I think you will see what I mean. Yes, milpitor, R10 must be in the circuit, else when V+ is applied there would be a direct short. Pin 1 is active lo until a positive going pulse is applied. R10 is a pull-down resistor that keeps it low, but also prevents a short circuit. Oops: I just saw another error. The connection between the ground side of C3 and the ground side of the buzzer should be eliminated. AllVol __________________ All those who believe in psycho kinesis, raise my hand. Last edited by AllVol; 6th February 2007 at 12:49 AM.

26th August 2006, 07:26 PM	(permalink)
philba	doesn't the new wire from the bottom of C2 short it out? also, the wires around /OE and LE look odd. not clear what's connect to what. Last edited by philba; 26th August 2006 at 07:30 PM.

26th August 2006, 09:19 PM	(permalink)
clifweb	Thanks very much the buzzer is now working. The only problem now is that I have to reset it manually. I was now thinking if there could be an addition part that could be later on added that when the buzzer is pressed a countdown will happen that could be preset but that it could be change with easily. Maybe having a + or – to increase or decrease the time. When the countdown hits 0 a sound will be heard to give the signal that the time is up. This unit will be separate of this circuit but has to be able to connect to it. Last edited by clifweb; 26th August 2006 at 09:37 PM.

27th August 2006, 04:06 AM	(permalink)
AllVol	Clif, Put R10 back into the circuit as it is supposed to be. With it not in line, you are shorting to ground when you press the reset button. AllVol __________________ All those who believe in psycho kinesis, raise my hand.

27th August 2006, 04:18 AM	(permalink)
AllVol	Hi, Phila, Actually, according to the original schematic, his C2 should not even be there. But it's not really doing anything as it is. AllVol __________________ All those who believe in psycho kinesis, raise my hand.

27th August 2006, 05:04 AM	(permalink)
clifweb	When I put R10 back the circuit is not working. As I remove it the entire circuit will work. Instead of the 22k I made it 1K and it work. Do you think that that is ok. C2 is present on the original schematic.

1st September 2006, 10:12 AM	(permalink)
clifweb	Done on bread board I have just built the buzzer on a breadboard to test it out before making it PCB. The circuit is working except that the 7 segment will only display the team number as long as that switch is pressed. Than it will be back to 0 after the switch is released. The buzzer is not working with the BC547 (As in the original schematic) the buzzer is not working at all but when instead of that I used the BC557 the buzzer kept on going the whole time. Can some one tell what he think is wrong.