Capacitor in Scamp LED Lighting Circuit?

[Wayne Carey]

When I connect my LED lighting circuit at the fuse block, it sparks. I measured the current. It is about an amp for a second, then it drops to 0. Does anyone know if Scamp buried a capacitor somewhere in the camper? I disconnected all the lights and the water pump. It didn't help.

[AC0GV]

Originally Posted by Wayne Carey

When I connect my LED lighting circuit at the fuse block, it sparks. I measured the current. It is about an amp for a second, then it drops to 0. Does anyone know if Scamp buried a capacitor somewhere in the camper? I disconnected all the lights and the water pump. It didn't help.

Is this original Scamp wiring or has someone re-wired it? Are you pulling just the light fuse and hooking the amp meter up in place of the fuse? The LP gas detector will draw more when first powered, but it should have its own fuse. Please let us know what you find.

[Wayne Carey]

This is original 2018 Scamp wiring. I measured the current between hot side of fuse and outgoing wire. There are 4 LED lamps and the water pump on the circuit, but it still draws current when all these are disconnected. CO is on separate circuit. It draws about 45 mA.

[Raspy]

Wayne,

I have no idea about Scamps, in particular, but a capacitor in the circuit is a suggested way to stop LED lights from blinking due to inductive coupling. LED lights draw so little power, and light so instantaneously, that they will blink from an induced current, where an incandescent lamp won't. My Black Series had this problem and blinked the running lights all the time the truck ignition was on. It was caused by the brake controller testing the brake wire circuit about twice a second with voltage spikes. Neither the light wires nor the brake wires were shielded and they ran next to each other on the way back. The fix for me was to run a new set of brake wires that were physically spaced away from the other trailer wiring. One fix that was suggested to me was to try a capacitor in the light wires that would absorb the voltage spike and keep the peak below the LED trigger point. In your case, if that is what is going on, I'd just leave it alone, as it won't cause a problem. Have you noticed that the lights take just a fraction of a second to come on, or that they continue for that same fraction of a second when turned off? LEDs typically come on much faster than incandescent lights.

[Wayne Carey]

I tried pulling the fuse with a light on. There seemed to be slight delay in turning off, like a capacitor discharging. If that's what I have, it would be nice to know where it is, in case it goes bad.

[gordon2]

Originally Posted by Wayne Carey

When I connect my LED lighting circuit at the fuse block, it sparks. I measured the current. It is about an amp for a second, then it drops to 0. Does anyone know if Scamp buried a capacitor somewhere in the camper? I disconnected all the lights and the water pump. It didn't help.

Are you sure there is nothing but LED lights on your "lighting circuit?"
By "it didn't help" do you mean that the initial current draw was still present?
BTW, it sounds like you are connecting the wiring to the fuse block with the battery (or converter) online, which is not good.

Originally Posted by Wayne Carey

I tried pulling the fuse with a light on. There seemed to be slight delay in turning off, like a capacitor discharging. If that's what I have, it would be nice to know where it is, in case it goes bad.

Any capacitor or anything that draws a little power and generates a small spark when you connect the wires will be in the bulbs, or the converter, gas alarm, etc. I suspect that the converter or something is still part of the system but the internals of the LED bulb (especially the better ones) can also cause them to take a second to dim. In any case I am sure there is no capacitor added outside those inside the various devices, and nothing to worry about replacing other than those devices (bulb, converter, etc).

[Wayne Carey]

Gordon,

There are four LED lamps and a water pump that I know of. I disconnected all of them and there is still a spark. I tried completely disconnecting the converter and there is still a spark. If I didn't at least leave the battery connected, I wouldn't know there is a spark.

Maybe there is a relay somewhere. I can hear a sound like a relay energizing but can't pinpoint the location. Scamp's diagram doesn't show anything additional.

Wayne Carey

[AC0GV]

Originally Posted by Wayne Carey

Gordon,

Maybe there is a relay somewhere. I can hear a sound like a relay energizing but can't pinpoint the location. Scamp's diagram doesn't show anything additional.

Wayne Carey

Mine is a 2017 and the only LED lights were the reading lights. Scamp is not one to keep the documentation up to date, but it sure sounds like a capacitor charging. Maybe someday when you least expect it, you will discover the device in question.
If anyone has a MODERN Scamp electrical diagram (WITHOUT A FLORESCENT LIGHT) maybe even with LED interior lights, please post it here or in the document section. Everything I found still has the florescent light shown.

[gordon2]

I don't think anything is unusual and I would not lose any sleep over it. I always suggest a master battery disconnect switch to make sure that any small continuous power draws do not discharge the battery when the camper sits unused for a weeks or months. Its also safer.

[Darral T.]

Someone's already mentioned "inductance". A coil in a motor can act like a capacitor. If you have an electronic circuit triggering a relay, they always put a diode across the output pins to block residual voltage from backing up into the circuit when it's powered off and damaging the circuit. That's one scenario.

My ears perked up when you said you thought you heard a "relay" click. If so, my idea is to look for it. If you can hear it, that will sure be easier to find than a capacitor.

I do have ONE more suggestion besides lookin for the relay. Look on your pump motor and see if they have a capacitor jumpered across the two terminals? Sometimes a capacitor is used that way to filter out "noise" from the motor. It would be worth a shot and easy to find if that's where a cap is going to reside.

I'd LOVE to know what you find WHEN you find it. With the LED's dimming slowly, you definitely have a small voltage "stored" somewhere in the line!

Originally Posted by Wayne Carey

Gordon,

There are four LED lamps and a water pump that I know of. I disconnected all of them and there is still a spark. I tried completely disconnecting the converter and there is still a spark. If I didn't at least leave the battery connected, I wouldn't know there is a spark.

Maybe there is a relay somewhere. I can hear a sound like a relay energizing but can't pinpoint the location. Scamp's diagram doesn't show anything additional.

Wayne Carey

[jimknoch]

Originally Posted by Wayne Carey

I tried pulling the fuse with a light on. There seemed to be slight delay in turning off, like a capacitor discharging. If that's what I have, it would be nice to know where it is, in case it goes bad.

Wayne Carey,
If you look at the electronics that are associated with each LED bulb, there are capacitors in their circuitry and each LED is actually operating on a fraction of a volt. So, yes, I would expect to see some capacitive inrush current as the individual voltage dividers on every bulb charge up and likewise a slow discharge as the power is switched off.

[Darral T.]

Come to think of it Jim, there MAY be a "transformer" somewhere to power the LEDs? If so, that would be where he's getting the slow discharge and the spark would be the transformer? Just a thought.

Originally Posted by jimknoch

Wayne Carey,
If you look at the electronics that are associated with each LED bulb, there are capacitors in their circuitry and each LED is actually operating on a fraction of a volt. So, yes, I would expect to see some capacitive inrush current as the individual voltage dividers on every bulb charge up and likewise a slow discharge as the power is switched off.

[jimknoch]

Originally Posted by Darral T.

Come to think of it Jim, there MAY be a "transformer" somewhere to power the LEDs? If so, that would be where he's getting the slow discharge and the spark would be the transformer? Just a thought.

Darral T, I had the impression that the LEDs were powered from his 12V system, like most RV lighting . There wouldn't be a transformer on a DC circuit. Now there could be some RF choke coils in the electronics to absorb and block any RF emissions from the LEDs, but they don't charge up like a power transformer would. Some of those tiny low voltage electrolytic capacitors may have quite a large capacitance (perhaps as high as several 1000uF).

[Darral T.]

True that. He said his pump motor which IS 12v. But, sometimes VR circuits can be available inline to bring it down from 12v to the 1-2v LEDs. But does his LED lights have their own circuit in eash bulb? Mine does.

Anyway, I'm using one (adjustable VR) to power a "Delay" circuit I built. Very efficient. Not sure I've seen it spark if I hook it up to 12v.

I would really like to know what/where IS the source of that spark and led dimming. FWIW, caps have been one of the more elusive "discrete" components to really understand in my electronic studies but I still love it!

Originally Posted by jimknoch

Darral T, I had the impression that the LEDs were powered from his 12V system, like most RV lighting . There wouldn't be a transformer on a DC circuit. Now there could be some RF choke coils in the electronics to absorb and block any RF emissions from the LEDs, but they don't charge up like a power transformer would. Some of those tiny low voltage electrolytic capacitors may have quite a large capacitance (perhaps as high as several 1000uF).

[Wayne Carey]

I got out my hearing aids and it sounds like it's in the back middle of the camper, below the table and behind the linoleum. It might be to keep city water out of the tank.

[jimknoch]

Originally Posted by Darral T.

True that. He said his pump motor which IS 12v. But, sometimes VR circuits can be available inline to bring it down from 12v to the 1-2v LEDs. But does his LED lights have their own circuit in eash bulb? Mine does.

Anyway, I'm using one (adjustable VR) to power a "Delay" circuit I built. Very efficient. Not sure I've seen it spark if I hook it up to 12v.

I would really like to know what/where IS the source of that spark and led dimming. FWIW, caps have been one of the more elusive "discrete" components to really understand in my electronic studies but I still love it!

Darral T.,
If i am not mistaken the actual LED is built into an oscillator circuit to keep it from overheating and deceive the human eye that it is on continuously. I remember building 7 segment displays back in the 70's and that was the trick to keep them from burning out too quickly, yet be bright enough.
If you're studying electronics, I can probably help you with an analogy for the capacitor function ... Lets assume you have a water system and you want the pressure to stay constant rather than going up and down as the pump starts and stops. In order to do this, you have an elastic rubber bag attached to the piping. As the pressure goes up from the pump, water flows into the bag and the elasticity will stretch until it equalizes with the water pressure at which point the water quits flowing into the bag. Now as water is used on the system decreasing the pressure, the bag contributes some of it's stored water under pressure, thus maintaining the pressure on the system. If the elastic bladder were suddenly removed, there would be a sudden surge of water coming out of it until it is equalized with ambient pressure. Now think of the capacitor in the same light, except instead of water and psi, you have electrons flowing under voltage (pressure), or amperage. So, initial charging of the capacitor would be just like the water flow into the rubber bladder. Discharging the water from the bladder would be like discharging the capacitor with a short circuit, hence a large current flow. A slow de-pressurization on either system would be a function of resistance to the current flow and the time it takes. This is know as the time constant. T=RC or Time(seconds) = Resistance(Ohms) x Capacitance(Farads). I hope that helps you visualize what a capacitor does in a DC circuit. Jim

[Raspy]

Originally Posted by Wayne Carey

I got out my hearing aids and it sounds like it's in the back middle of the camper, below the table and behind the linoleum. It might be to keep city water out of the tank.

Do you mean as an electric backflow preventing valve? That duty would be handled much easier and better with a simple mechanical check valve. There is no reason to do it electrically that I know of.

The typical way the city water is run into the system is to T the city water into the cold supply to the trailer just after the water pump. The pump functions as a check valve and an additional mechanical check can be added in the line, after the pump, and before the T, for insurance. When running on pump pressure, a mechanical check on the city supply line prevents pressure from backing out the city connection point. No power needed for any of that, except the pump.

[Raspy]

A bit off the subject, but one place where capacitors are needed is on the conveyor belt motors that advance your groceries toward the cashier in markets. Have you ever noticed that some of them start and stop very abruptly, tipping over taller items like wine bottles with the sudden jerk? A capacitor smooths the start and the stop of motors by absorbing some of the power on startup and delivering it to the motor during shutdown. Like a battery being charged and discharged, the power absorption/delivery is spread over a bit of time, so the motor "soft" starts and "soft" stops.

[Wayne Carey]

I disconnected the outlet hose from the pump and was able to blow and suck air through it with and without the fuse in the circuit, so it's not a solenoid. I'm not rearing the trailer apart to find it although I'm pretty sure it's in the wall at floor height in the middle of the back of the camper.

[Wayne Carey]

I'm embarrassed to admit this, but it was the exhaust fan. Thanks for all of your help. For some reason, I thought the fan was 120 Volt, AC.