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I have a MSTJRY touch kitchen faucet purchased through Amazon. It uses a valve solenoid in line with the water supply to control the on/off of the faucet based on capacitive touch on the faucet stem. There is one black wire that connects the solenoid to the stem (I'm assuming this is the capacitive sense wire). It works extremely well when using the 4AA batteries. What I'm wanting to do is convert that 4AA batteries into house power (standard outlet). I tested the 4AA battery output to make sure they were wired in series producing 6V DC. I found a old 2 prong 6V 1A AC/DC adapter and spliced the wires accordingly, replacing the battery power pack. I tested the AC/DC output on my multimeter and got 6V DC. When I plugged the solenoid into the modified AC/DC adapter (house power), the capacitive touch solenoid went crazy and started randomly firing. The house power outlet is not isolated as there are other devices on the circuit which I'm assuming is causing noise. Delta has a similar faucet technology called Touch20 with an optional power adapter (Delta EP73954). The only difference I see in that power adapter vs mine (besides 6V 1A vs 9V 1.5A) is the use of a grounding pin (3 prong). Any help would be much appreciated.

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  • \$\begingroup\$ You could try with a different adapter, preferably one rated for 1.5A like the manufacturer's model. Some of those wall warts have an extremely gross output even though they look OK on a multimeter. A thrift store like Goodwill or Salvation Army should have a pedigree selection of adapters for a buck or two. \$\endgroup\$ – vir Mar 1 at 23:29
  • \$\begingroup\$ Be aware that there are a wide variety of voltage converters of varying quality that could be inside an adaptor marked "6V 1A". Especially for really old ones or ones designed for a constant load, they can be as simple as a transformer, rectifier and capacitor. I'd check a few pawn shops for newer and "nicer" adaptors and try a few of those before I try troubleshooting one that for sure has problems. \$\endgroup\$ – K H Mar 2 at 1:42
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There are a few issues that might cause the relay "chattering":

  • If the "wall wart" (power supply) is poorly isolated from the mains, AC could be getting into the sensing circuit.
    • Remedy: try a different type of power supply.
  • If the power supply is high-efficiency, e.g., using high-frequency PWM to control output voltage, some radio-frequency interference may be causing the issue.
    • Remedy: try a different type of power supply.
  • The power supply might not provide enough current for the demands of the solenoid.
    • Remedy: Put a large electrolytic capacitor or a supercapacitor across the supply. Mind the polarity and voltage requirements, particularly for the supercapacitor. Or try another suply, with higher current rating.

N.B. To reduce the danger of electric shock and of fire because of current flow to ground, use a grounded power supply.

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    \$\begingroup\$ Found a different 6V AC/DC adapter at goodwill and it worked fine. Thank you for the suggestions. Didn’t know that adapters make a difference. \$\endgroup\$ – mjhuffer Mar 3 at 2:02

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