Here is a question on implementing a relay based soft start and trying to avoid arcs within the relay. I'm switching the AC voltage coming out of the wall, so want to do this correctly. I've got a delay circuit and will implement the soft start as shown on the attached schematic....I think, so I wanted everyone's input.
Here is the schematic:
Its intended to work like this-
1. When the amp is turned on the relay is connected as shown with a resistive soft start element (resistor or thermister or combo of both) in line with one primary of the transformer to prevent a surge.
2. After a time delay, S1 is activated and the 12VDC circuit provides 12VDC to the relay, causing the relay to switch, which connects the primary of the transformer directly to the AC inlet, bypassing the resistive element.
I'd like to prevent arcs within the relay when this switching happens. I heard you all use capacitors for this, which is why I'm thinking of using C2 and C3. C2 would prevent the initial arc, and C3 would prevent an arc when the amp is turned off and the relay returns to its initial state....I think.
D1 is to prevent voltage from relay actuation from interfering with the control circuit. I'm not sure what C1 is for, but I've seen people use a cap here.
3. My question is -- do I have this right? Are D1, C1, C2 and C3 necessary, will this setup prevent relay arcing? Are the C values correct? If not, what will?
Here is the schematic:
An externally hosted image should be here but it was not working when we last tested it.
Its intended to work like this-
1. When the amp is turned on the relay is connected as shown with a resistive soft start element (resistor or thermister or combo of both) in line with one primary of the transformer to prevent a surge.
2. After a time delay, S1 is activated and the 12VDC circuit provides 12VDC to the relay, causing the relay to switch, which connects the primary of the transformer directly to the AC inlet, bypassing the resistive element.
I'd like to prevent arcs within the relay when this switching happens. I heard you all use capacitors for this, which is why I'm thinking of using C2 and C3. C2 would prevent the initial arc, and C3 would prevent an arc when the amp is turned off and the relay returns to its initial state....I think.
D1 is to prevent voltage from relay actuation from interfering with the control circuit. I'm not sure what C1 is for, but I've seen people use a cap here.
3. My question is -- do I have this right? Are D1, C1, C2 and C3 necessary, will this setup prevent relay arcing? Are the C values correct? If not, what will?
OK I think i get what you are saying. You are saying that the relay should just short out the resistor or thermister. What about this:
An externally hosted image should be here but it was not working when we last tested it.
The schematic shows the initial condition. After a time delay the switch will flip causing the relay to change states. Thus, when the time delay is over, the relay simply shorts out the resistor or thermister, leaving it in the circuit. Is this design better? Is C1 required or harmful (what value should it be?)
One of the reasons I take the trouble to do DIY is to interact with everyone and try to learn concepts that seem interesting, such as this one. I don't care if it lasts 20 years, I'd still be interested to learn about how to construct a soft start that doesn't arc.
Besides, I can't tell if you are indicating that the 1st or 2nd one would last 15 years, as its not stated.
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