12V test light result problem ??? :confused:

[steptoe]

Yep, confused.

I am in need of xpert help on this one.
The LED 12V tester type you hook up to the battery first




, lights up both a green LED and a red LED until you touch the probe to either power



^^^^^^^believe it, this LED is red bfore digital photography got to it ^^^^^^

,or ground , if you got ground the red goes out



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, green brighter? or if touch to power, green goes out and red brighter.

PROBLEM : is when I touch to what should be pos power out of my power adaptor down to 7.5 V the red LED dims! and green still lingers....


you know how a problem shared is a problem halved ? I may have worked it out - the output is set at 7.5 V , maybe if I shift it up to 9V or 12V if possible the green may go away

NOPE, not it...

story continues

Using a powertech voltage adaptor plugged unto a cig lighter attached to a small 12V sealed lead acid battery SLA



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Testing the output of the adaptor firstly to determine polarity need pos to centre tip +

I have definitely got a bold green only LED on the outer of the plug



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but when I touch the centre tip red LED dims rather than go brighter and green stays on.
I threw an Ohms resistance wheel



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into things to see and depending on rating there the green LED glimmers or just goes out, leaving red to glow nicely.
Side note is if I use the old Subie lighter socket, I don't get a green operating light on the adaptor. Touch the battery direct to adaptor and yes green function light on



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this glimmers or pulses when I have test lead on the pos tip too !!
Change power supply direct to battery does not solve problem either ??

Any genius's are welcome to comment

all in readiness to set up a battery powered cctv camera at an "outpost"

did someone say try a diode??

think there is one on a bench somewhere......

[steptoe]

nine images not allowed

so here:



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[steptoe]

battery itself tests to 12.7V

Lighter socket tested to give out only 9.9V of that (somehow?)


a diode ( I promptly dropped in a darkened shed before testing ) did not fix when shoved at tip end of wanted 9 or 7.5V

[steptoe]

if in doubt just chuck it all together and hope for best outcome not being a frazzled wireless camera

HEY, HEY !!

Sometimes 2 + 2 = 5

Must be time to check last nights lotto entry

[fredsub]

best way to look at it is the device tests the difference between the supply leads of device and the test point.
Example
so if supply at 12V and test at 12V => Red Led
11.5 => Red dimmer, maybe bit of green?
test at 0V => Green Led
0.5 => Green Dimmer and maybe red start glowing ?

I think your test device is cheap & crude, nevertheless does seem to indicate where you have full +V or 0V. Other readings mean your getting
at the +V through some resistance, or the 0V through some resistance
and not proper ground. The quantity of that resistance is not important,
its just to tell you don't have the full connection.

Have a device with similar purpose, only has flashing leds. so full +V, full red
led, less than +V, then Red flashing, aka at 0V, Green, > 0V Green flashing.
I use it alot for debugging electrical s on car, as its more useful than a voltmeter.

[steptoe]

It was a cheap and nasty little test light but I got used to hooking it up to battery first, always testing before next job at hand and have grown to respect it for what it is. One step better than my crude old brass test light and pointy bit.

[pitrack_1]

Steptoe,

1) The cigarette lighter is putting out 9.9V (let's say 10V) n'est-ce pas? The input specification to your voltage converter MP3014 is 11-30V. So this is below spec and probably why the green LED on the voltage converter doesn't light. It may also not be working properly as a result of the low input voltage.
2) You need to check whether the output of the MP3014 is floating or grounded to the vehicle. You can do this by a continuity check between the MP3014's negative input and the negative output (if common ground/negative can be assumed). Does the MP3014 feel 'heavy' like it has a transformer (probably not nowadays)? If so, then it could have a common ground. If it feels 'light', like mostly plastic rather than having iron inside, then it's a switchmode based unit. The output will probably be 'floating', i.e. untied and unconnected by a ground/negative, with reference to the input.

Why is this important? The green/red LED tester is probably comparing voltages between the probe and the +/- inputs. This only works if the voltage tested on the probe is directly related to the input voltages. A floating output isn't.

A couple of other notes:

A) The 9.9V output of your cigarette lighter plug either means it's faulty or it is designed for that voltage perhaps e.g. for some proprietary cigarette lighter (and to prevent generic ones working properly which would be designed for 12V). Wouldn't put it past Subaru given their other wiring shenanigans. There is no illumination light wired into it is there? That could also account for the voltage drop- the illumination may only work when there was enough current draw (cigarette lighter inserted) perhaps.

B) Switchmode power supplies operate at high frequencies to generate the DC voltages required. They (especially cheapies) can/do have high frequency components leak onto the output and can interfere with electronic equipment. It's not impossible for this power supply to interfere with either the operation of or communication of the camera you connect it to (I'm not saying it will). I have known electronic devices to specifically state not to use a switchmode power supply with them. You may be able to reduce any noise by winding the power supply cable to the camera around a ferrite ring (or put it through one of the snap-on ferrite beads, also from Jaycar e.g. LF1250/LF1256/LF1258/LF1260). Don't put a ferrite bead on the camera output, it'll suppress the signal

Hope this is of assistance and not confusion!

Happy New Year!

[steptoe]

Thanks guys - all advice great, well written and now better understanding of the problem. Now recall seeing a relay spitting out confusing signals for split second or until a unit was attached to it and whole circuit working as planned, so making more sense.

This unit did have a lit ring fitted prior to me pulling it down to basics.

This camera, a few SLA batteries in parallel on top of each other, another socket and some wires are planned to disappear down a 100mm square steel tube with a solar panel out of reach above - masquerading as a garden solar light post , hoping it will transmit to my DVR unit on motion detection mode.
Not sure if the cameras little wireless aerial is gonna transmit through the 2mm tube or an external antennae is needed yet.

Found a 10W solar panel from the solarsupplystore or whatnot $45 delivered, about half the jcar price
Will post up finished results - nabbing the vandals of the 'hood (may need to learn to pixelate their faces !

[pitrack_1]

Not sure if the cameras little wireless aerial is gonna transmit through the 2mm tube or an external antennae is needed yet.

Should be fine if the tube is plastic. Metal will block the signal. Easy to test anyway!