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| Need some help building a circuit involving switchs and relays |
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| Renate:
The 1N5225 are 3.0V Zeners. That means that the peak voltage across the triac should be 3V before it fires. It sounds like the thermistor has failed with a high resistance. Measure the resistance in-circuit (it should be so low that the other stuff doesn't matter). I would expect the resistance to be less than an ohm. The point of the thermistor is for protection. If you want to try as a test replace the thermistor with a 10 ohm 1/2 watt resistor. This is not a safe or a permanent replacement. (The resistor will burn up if you have a short in the feeder cable.) Or you could just put in a 1A fuse. You know, the triac is good for 16A, you said the supply was 6A? There is no reason anything should be complaining at 50 mA. |
| Shaydzmi:
I'm sorry I didn't see your reply until now. --- Quote ---Measure the resistance in-circuit (it should be so low that the other stuff doesn't matter). --- End quote --- I didn't understand what you mean. --- Quote ---The point of the thermistor is for protection. --- End quote --- To protect what? what are the things that may be damaged if no thermistor is installed? --- Quote ---Or you could just put in a 1A fuse. --- End quote --- Maybe I'll do this, but I think that if the fuse blows up, the machine won't stop if a yarn is broken. --- Quote ---You know, the triac is good for 16A, you said the supply was 6A? --- End quote --- Yes, actually the transformer supplying the board has 2 ouputs (24V 4A) and (24V 8A), but I don't which one is which, because no labels are on the transformer anymore. --- Quote --- the triac is good for 16A --- End quote --- Can you please explain to me what does the triac do exactly in this circuit? |
| Renate:
--- Quote from: Shaydzmi on June 02, 2020, 08:46:17 pm --- --- Quote ---Measure the resistance in-circuit (it should be so low that the other stuff doesn't matter). --- End quote --- I didn't understand what you mean. --- End quote --- Take your meter and measure the resistance of the thermistor without un-soldering it from the circuit. It should probably be almost a dead short so that the value of the other components hardly matter. As I've said, the triac is the main piece that feeds the light bulb current. If it's not working correctly, then the only current to the lightbulb is through the 470 ohm resistor. That would make the bulbs glow dimly and not work at all when 10 bulbs were on. I never said to leave the resistor or fuse or anything in circuit permanently. I only meant to use it as a test to prove that the thermistor is bad. Just measure the thermistor, ok? |
| Shaydzmi:
--- Quote ---Take your meter and measure the resistance of the thermistor --- End quote --- It measures 103.9 \$\Omega\$ . --- Quote ---As I've said, the triac is the main piece that feeds the light bulb current. If it's not working correctly, then the only current to the lightbulb is through the 470 ohm resistor. --- End quote --- Probably that's the case. How can I measure the triac to know if it's working or not? |
| Renate:
100 ohms is far too high for a cold thermistor. It's bad. Consider a single bulb on that (50 mA) it would drop 5V. But it would also get warm and the resistance would even be higher. The point of the thermistor is to protect if one of the feeders or the cable got shorted to ground. You want to limit the current in such a case. The triac is not broken open because the thermistor gets warm. It might be shorted (but I don't think so). If it were shorted the lights would work, but the relay wouldn't. As I said, replace it with a low value resistor or a fuse as a test. The bulbs should be bright and the relay should trigger correctly. |
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