Chicken & Egg Stand-By SSR Kick Voltage Solution(s) - Page 1
Forum section: electronics / general

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: May 11, 2025, 11:08:24 pm
content: "So here's the deal" as they say....I have a SSR that will accept a control of 3.2VDC to 20+VDC that is working just fine except for the initial starting voltage. (Touching of a 9V battery)It's the old chicken and egg problem.In order to start the SSR to turn on the device a transformer of 1A-2A AC, it has to come up from a standby source.Once energized it provides its own voltage to keep running.A mechanical rod to a magnetic hall effect switch is actuated and sustained until it moves the mechanical rod to off.One needs the initial DC to power the KY-003 module which is connected as open collector to the SSR's return to ground path.All of it is at about 9VDC.That's the chicken.The egg is where does the 9VDC initially come from!I thought about a separate transformer for which space prohibits. An ML2032 coin cell with charging circuit. An 18650 with the TP4056. A 1F 5.5V super capacitor. A 3.7V 70mA LiPo battery.THE BIGGER QUESTION! How long would each solution last energizing the KY-003 and SSR, and then remain off line for months, days etc before discharging and rendering the startup null?What would be the best way for the "egg"? No external cables or wires are allowed only the voltage from the device to be started.I await you with your most appreciated answers.

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: May 11, 2025, 11:21:02 pm
content: Example items:SSRhttps://www.amazon.com/SSR-40DA-3-32VDC-Output-24-480VAC-Plastic/dp/B08GPB7N2TLiPohttps://www.amazon.com/YTKavq-Battery-Lithium-Rechargeable-Connector/dp/B08TTTJGQ7KY-003https://www.amazon.com/Ferwooh-3-3V-5V-KY-003-Effect-Magnetic/dp/B0CYYZZDSTSuperhttps://www.amazon.com/PATIKIL-Capacitors-Capacitor-Resistance-Consistency/dp/B0DDY3T5YMTP4056https://www.amazon.com/HiLetgo-Lithium-Charging-Protection-Functions/dp/B07PKND8KG

author: bdunham7
author_rank: Super Contributor
timestamp: May 11, 2025, 11:30:49 pm
content: How much current does the KY-003 draw in standby? I presume that's the entire issue right there because otherwise the solution is extremely simple.

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: May 11, 2025, 11:35:22 pm
content: Unknown yet as I haven't been able to measure it yet.I would assume only 2 LEDs so 40mA max.The IC in the KY-003 standby current draw would be the issue as nothing LED is "ON" until the sensor is mechanically actuated. I would assume standby leakage or maybe nothttps://makerhero.com/img/files/download/3144-Datasheet.pdf

author: amyk
author_rank: Super Contributor
timestamp: May 12, 2025, 01:58:04 am
content: Resistive or capacitive dropper?

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 12, 2025, 03:15:07 am
content: Assuming isolation from the AC supply is needed, a Y rated capacitor, while not "isolated" in the strictest sense, is certified to safely bridge between AC mains and low voltage. Rectify the tiny bit of current to charge a capacitor and you'll have your standby supply that's compact and low cost.

author: bdunham7
author_rank: Super Contributor
timestamp: May 12, 2025, 03:39:06 am
content: Quote from: Quarlo Klobrigney on May 11, 2025, 11:35:22 pmThat datasheet shows a supply current of 4-5mA in the off state, so no small battery is going to supply that for months on end.Here is a question I posed to Co-Pilot:What is as good design for a capacitor dropper circuit providing 10mA from 120VAC?And here is the answer:A capacitor dropper circuit is a simple and efficient way to derive low-current DC from high-voltage AC without using a bulky transformer. For a 120VAC supply and a 10mA output, here's a basic approach:Design Considerations:Capacitor Selection – Use an X-rated capacitor designed for AC applications. The reactance 𝑋𝐶is given by:𝑋𝐶=12𝜋𝑓𝐶where𝑓=60𝐻𝑧(for mains power in the U.S.).Voltage Regulation – A Zener diode or a low-dropout regulator can stabilize the output voltage.Current Limiting – A series resistor can protect against inrush currents.Rectification – A bridge rectifier converts AC to DC.Filtering – A capacitor smooths out the rectified waveform.Example Calculation:For 10mA output, assuming a final DC voltage of around 12V:Required reactance:𝑋𝐶=120𝑉/10𝑚𝐴=12𝑘Ω.Capacitance𝐶=12𝜋×60𝐻𝑧×12𝑘Ω≈0.22uF.Use a safety-rated film capacitor, typically X2 type.A bridge rectifier will convert AC to DC.A Zener diode (e.g., 12V, 1W) will regulate voltage.Would you like a specific schematic or component suggestions?

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: May 12, 2025, 10:45:46 am
content: You mean𝑋c=1/(2𝜋𝑓𝐶)I would be very worried making a line powered supply.I did think briefly, very briefly about such a prospect before asking here.My first concern is that one side of the we will call it "startup supply" would be connected to frame ground.The other is frequent daily violent lightning that usually destroys anything attached directly to the mains like that and safety would be the concern let alone turning the unattended device to onYour suggestions are all valid but I would like to find a low voltage solution if possible due to my fear the factorChina supplied capacitors and all that, shades of Rifa caps.A battery or second supply not directly connected with capacitors to the line would be my safety factor at my age.If charge longevity is an issue, would an 18650 be a better solution?I will check the standby "vampire" current of what is operating right now.As previously stated, the DC after the device gets started is free wheeling.It just needs a kick in the ass to move.

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: May 13, 2025, 02:18:06 am
content: Checking some voltages today:Actual circuit supply DC 9.31VThe SSR-40DA 11mA when on.The KY-003 Hall Effect 2.4V @ 8mA when on.I actually found a DST-4-16 transformer but where and how to mount it is the issue.https://belfuse.com/media/datasheets/products/transformers/ds-st-st-series.pdfAny ideas?