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| spdt switch |
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| fixit7:
--- Quote from: Audioguru on May 21, 2019, 07:28:42 pm ---The switch is faulty because its contacts are made for up to 300mA at 125VAC (peak voltages are 177V). But again, your schematic does not show the resistance value of R1 which probably has a current that is 1 millionth what the switch needs and your pin 2 voltage is 60 times too low for that high power switch. Use a switch with gold contacts made for low power. Is the function of the switch to turn off the beeper when you want after it has been triggered? --- End quote --- Resistor is 220 ohms. Switch does turn off beeper when it is triggered. |
| Zero999:
Why not put the switch in series with the entire circuit, rather than just the beeper? Audioguru is mistaken about switches corroding, when the current and volt are too low. Using a switch at too lower voltage and current will not break it, but he does have a point that it might be unreliable. Switches with copper or solver contacts need to have a high enough voltage and current to ensure the oxide layer is broken, when the contacts make. This is known as the wetting current. If the current is too low, then the switch might not operate reliably. The solution is to use a switch with gold plated contacts, which doesn't suffer from this issue because gold doesn't oxidise. |
| Brumby:
It's a slide switch. The mechanical action of contacts sliding should be more than enough to break any oxide layer unless it is excessive. Long term storage in less than ideal conditions could cause that. Then there is the possibility of other contaminants getting onto the contact surfaces. Both of the above conditions can sometimes be rectified by operating the switch several times, possibly in conjunction with a switch/contact cleaner. If this doesn't fix things, then the switch would seem to have a more severe mechanical fault. The other thing you can do (if you haven't already) is to try the two combinations available (centre and left -or- centre and right) and see if one is reliable. |
| fixit7:
--- Quote from: Zero999 on May 21, 2019, 08:42:58 pm ---Why not put the switch in series with the entire circuit, rather than just the beeper? Audioguru is mistaken about switches corroding, when the current and volt are too low. Using a switch at too lower voltage and current will not break it, but he does have a point that it might be unreliable. Switches with copper or solver contacts need to have a high enough voltage and current to ensure the oxide layer is broken, when the contacts make. This is known as the wetting current. If the current is too low, then the switch might not operate reliably. The solution is to use a switch with gold plated contacts, which doesn't suffer from this issue because gold doesn't oxidise. --- End quote --- I am not sure how to put the switch in series with the circuit. The switches connects with pins 2 and 3 of the 555 chip. |
| Brumby:
The suggestion means joining pins 2 and 3 of the 555 and putting the switch in the power to the circuit so that the whole circuit is turned on or off. |
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