Circuit to alert when 2 button push at the same time

[Dukey]

Hi,

I have a large switch panel with 13 switches, I want to set some alert when any
2 bottons are push in the same time (it's ok to have the signals comes in the same time)
I only want a buzz sound to warn the user to return one finger.

I want to ask for a idea to make this circuit, now I'm thinking of using large OR-gate
array those switch together, but it seems the be a hard work.
Do I have a better way, or if OR-gate is suit what No# should I use

Thank you,

 

[IanP]

This is a typical job for a small microcontroller ..
Use its 13 pins as inputs and 1 pin as output to an audio alarm buzzer ..
Microcontroller should sequentialy scan 13 inputs, say every 5ms, and if it descoveres more than one input at LOW stage it will generate a square wave for as long as this situation persists ..
Regards,
IanP

 

[Dukey]

Thank you,

I'm looking for not to use microcontroller. Just for maintenance reason.

Are there simple circuit by Logic-gates ?

 

[echo47]

That would take a lot of gates.

If your buttons have pull-up or pull-down resistors, then use an analog comparator to monitor the total current. If each button draws 1mA, then sound your buzzer when the total current exceeds 1.5mA.

 

[neoaspilet11]

Thats simple! Try this

y = s1s2+s1s3+s1s4+s1s5+s1s6+s1s7+s1s8+s1s9+s1s10+s1s11+s1s12+s1s13 + s2s3+s2s4+s2s5+s2s6+s2s7+s2s8+s2s9+s2s10+s2s11+s2s12+s2s13
+ s3s1 +s3s4+s3s5+s3s6+s3s7+s3s8+s3s9+s3s10+s3s11+s3s12+s3s13
+ s4s1+s4s2+ +s4s5+s4s6+s4s7+s4s8+s4s9+s4s10+s4s11+s4s12+s4s13
+....
continue the pattern until you get

+s13s1+s13s2+s13s3+s13s4 +s13s5+s13s6+s13s7+s13s8+s13s9+s13s10+s13s11

You see its a huge gate array. Belive me you get a lot of headaches if you want to implement this one. And the it will give a logic HIGH if two or more switches are pushed. If you want only just two switches to make it active, thats a different and complicated equation.

I suggest use a microprocessor. It is simple and economical to use

 

[mike65535]

Depending on how your switches are wired up, perhaps you can use some sort of analog circuit?

I'm thinking some sort of series resistor, in-line with each switch, so that when the switch closes, there's a small voltage developed on the R. Then across each R, use an opamp/comparator to sense/amplify that, and sum the outputs of all the opamp/comparators in another single opamp so that its output goes high when there's more than one sense voltage present.

[edit] I see echo47 wrote something similar![\edit]

 

[aNdreiBuuu]

Yap mike has a good ideea...
try some similar of this design...
//a

 

[jeffttan]

if the voltages involved are small, you can use a summing amplifier for your circuit.... place the switches on each input of the summing amplifier then if the output voltage is greater than that of one, a comparator enables the buzzer.

 

[jeffttan]

if the voltages involved are small, you can use a summing amplifier for your circuit.... place the switches on each input of the summing amplifier then if the output voltage is greater than that of one, a comparator enables the buzzer.