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Please bear with me as I am a complete beginner. I am planning on using a PTC heating element in a project. Here is the link to the one I bought on Ebay: Aluminium enclosed 12V 80W PTC Heater/Heating Plate ~175℃ Max Temperature. To power it I bought this power supply: SHNITPWR 3V - 12V Power Supply. I connected the power supply to the heating element using the DC terminal connector, as pictured: Photo of the PTC element connected up

I set the power supply to 12V. When I turn it on the PTC does not get hot or change in temperature at all -- although I can feel a slight static charge on it. My multimeter measures 12V on the DC connection terminals when the PTC is disconnected, but 0V when it is connected. Is anyone able to explain what I'm doing wrong? I've provided as much info as I have, but please let me know if there is anything else I need to check. Thank you!

mikefsway
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    What is the measured resistance of the heating element when cold? My guess is that it's so low that it'll use much more then the stated 80W initially, tripping the power supply's protection. – Unimportant Feb 18 '22 at 14:33
  • This is why pro engineers don't buy from pee-bay or shamazon of mali-express or bang-bad - lack of details and lack of a traceable quality line to a reputable manufacturer. [What to check for when buying an electronic component or module](https://electronics.stackexchange.com/questions/504044/what-to-check-for-when-buying-an-electronic-component-or-module). – Andy aka Feb 18 '22 at 14:33
  • @Unimportant I believe it is 6 Ohms. At least when I set my multimeter to the 200 Ohm setting and measure across the PTC, it reads 6. I'm sorry, I'm a complete beginner -- is this lower than expected? – mikefsway Feb 18 '22 at 14:40
  • @Andyaka Thank you, will look out for that. I don't suppose you have a recommendation for a PTC or power supply manufacturer? – mikefsway Feb 18 '22 at 14:42
  • That's much higher then expected. 6 Ohm @ 12V would result in only 24W. – Unimportant Feb 18 '22 at 14:52
  • Sounds like your power supply is tripping due to OCP. What’s the current rating on it? – winny Feb 18 '22 at 14:53
  • @winny Thanks -- it says 10A Max on it. – mikefsway Feb 18 '22 at 15:00
  • @Unimportant Thanks. I might have thought at 24W it would still heat up a bit. – mikefsway Feb 18 '22 at 15:01
  • It should, but is that measurement correct ? The device is rated for 80W, so it should be much lower then 6 Ohm when cold. – Unimportant Feb 18 '22 at 15:04
  • Maybe your current limit on the power supply is set too low. – Andy aka Feb 18 '22 at 15:05
  • @Unimportant Thanks -- I will try to check. – mikefsway Feb 18 '22 at 15:08
  • @Andyaka Thanks -- I did wonder about this, but it doesn't seem to be something I can adjust (there is only a knob to set the voltage). – mikefsway Feb 18 '22 at 15:09
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    Gawd, you'd think they would clean up the hand hacksawed ends of that heating element with a file before they had the nerve to sell it. –  Feb 18 '22 at 15:09
  • Are both metal ends of the wires making good contact with the plug? Looks like one might not be making contact. Even at 6 Ohms, it should still get warm/hot. – rdtsc Feb 18 '22 at 15:15
  • @rdtsc Thanks -- yes, they are -- I just trimmed one a little shorter than the other (was planning to even up after initial test). – mikefsway Feb 18 '22 at 15:16
  • The power supply is likely tripping out due to overcurrent. It's not a reputable supply, so it may say 10A even if it cannot actually supply that. – Drew Mar 27 '23 at 14:59

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If you have a multimeter, set it to a DC volts scale near 12V (as applicable) and touch the probes to the wires while it should be operating:

  • Zero Volts: The power supply is not working at all, or there is a connection issue.
  • Steady low Volts or oscillating low Volts: The power supply is unable to power this load, so is shutting down repeatedly. Could be a bad supply, or just incapable of powering this load (which would likely be false labeling because it claims it is rated for 10 Amperes of current. 10A * 12V = 120 Watts of power. You are attempting to draw 12V/6Ω = 2A * 12V = 24W and it fails.)
  • 12V definitely going to heater: The heater is defective, or in the case of it using semiconductor devices inside, it is externally or internally wired in reverse, which could block all current flow. In that case, try reversing the wiring and try again.

Note 12V is "safe" to touch and tinker with, meaning that touching it will not hurt you, but it can still make things (like a heater) very hot. Voltages >50V are considered dangerous to touch, and mains voltage (120V or 240V) even more so. Happy experimenting!

rdtsc
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  • Thanks! Weirdly, it just started working temporarily (i.e. element got hot), but has now stopped again -- and stopped before I could measure voltage. I can confirm multimeter shows 12V when PTC disconnected, and 0V when connected. – mikefsway Feb 18 '22 at 16:09
  • The heater could possibly be "shorting" inside, where the wires accidentally touch each other. In that case, the power supply *will* shut off and retry continuously. Usually this makes a faint clicking sound in the power supply. – rdtsc Feb 18 '22 at 17:36
  • thanks, will investigate – mikefsway Feb 18 '22 at 20:31
  • Try running the heater at a lower voltage this will not cause any damage (it will cause less heat however) . the power supply looks kind of small for its claimed 120W capability. – Jasen Слава Україні Feb 20 '22 at 12:30
  • Thanks @Jasen, will try! – mikefsway Feb 23 '22 at 12:29