Converting Spotlight Power Supply

[Per Hansson]

Re: Converting Spotlight Power Supply

New thread is here: https://www.badcaps.net/forum/showthread.php?t=71018
Please stj and Curious.George try to not derail threads, it's 30°C here and I could be at the beach instead of this

[sambul83]

Re: Converting Spotlight Power Supply

Lets move the discussion about power grids in US and UK to a separate thread it deserves. Otherwise it creates chaos in this thread as obvious offtop making it hard to find useful info on topic for any reader. Asked the moderator to separate threads.

[sambul83]

Re: Converting Spotlight Power Supply

I keep 4 boxes (approx the size of a case of beer) labeled 5V, 12V, <12V (i.e., 5-12) and >12V and just replace the connector, as necessary, to get the configuration that I need.

Power adapter I use now is 5V rated, but it actually heats up more when hooked to the Buffalo router compare to the lamp. Can someone link a cheap power supply in 2-5A range with manually adjustable voltage that can feed the lamp and other similar things in 5-12V range?

Also, can you guys link a very bright low cost compact flashlight as a replacement of this spotlight? I don't care about "tactical military" marketing crap, just real high LM figure.

[Curious.George]

Re: Converting Spotlight Power Supply

The modded spotlight draws 3A at 5.4V with both lamps lit, meaning at 6V it'll draw 2.7A.

Only "approximately".

The 3A figure suggests that the resistance of the lamp filament is about 1.8 ohms (5.4V/3A) AT THAT FILAMENT TEMPERATURE. If this remains substantially unchanged, at 6V you'll see 6V/1.8ohm= 3.3A.

Said another way, at 5.4V you're dissipating 16.2W (5.4*3) in the lamp. At 6V, you may see 20W (6*3.3). As this will likely raise the temperature of the filament, it's resistance may climb a bit leaving you with slightly lower current/power consumption.

The adapter is slightly heatup now, I wonder if it limits the passing current as its a Buffalo Wireless router adapter, i.e. smarter than generic CN gear? The main lamp is likely a bit lower power rated than 25W figure I found on the web, unless the adapter limits power, possibly to prevent "router" damage?

The adapter likely has some form of current limiting built in (assuming it is a regulated supply). This will be obvious if it really is a "6V" adapter yet is only developing 5.4V at that load current.

"Heating up" suggests the adapter is already "working hard" (for its capacity).

For a short term test, you can momentarily put 6V of battery (even 4 "D" cells) to act as a supercap on the output of the 6V power supply and connect the lamp to check the actual current draw at 6V. I.e., the bulk of the power is delivered by the adapter with the batteries (quickly depleting) to satisfy the shortfall.

(This assumes the adapter really is trying to deliver 6.0V and the battery pack is roughly the same nominal voltage)

Once you know what the lamp draws AT the rated voltage, you will know how large the adapter needs to be to ensure it supplies enough power for the lamp without sagging.

[Sorry, I can't think of any alternative suggestions for a handy 6V power source... maybe a motorcycle battery?? Surgery on a 12V battery to expose the connections between cells 3&4?]

N.B. This sort of thing is the motivation for "collecting" various wall warts/bricks. I keep 4 boxes (approx the size of a case of beer) labeled 5V, 12V, <12V (i.e., 5-12) and >12V and just replace the connector, as necessary, to get the configuration that I need.

[eccerr0r]

Re: Converting Spotlight Power Supply

The modded spotlight draws 3A at 5.4V with both lamps lit, meaning at 6V it'll draw 2.7A.

As there is no constant power regulator, the draw will be 3.3A at 6V. This is actually less than the 25W figure.

I'm hesitant to test the spotlight with a 12V adapter.

You should be. It will immolate with that voltage if the power brick can supply the current.

[sambul83]

Re: Converting Spotlight Power Supply

Insert your ammeter into the circuit to see exactly how much power is being drawn by the lamp (power = volts * amps) at that 5V level.

Since the thread is apparently still alive, let me interrupt your happy exchange with more relevant info. The modded spotlight draws 3A at 5.4V with both lamps lit, meaning at 6V it'll draw 2.7A. The adapter is slightly heatup now, I wonder if it limits the passing current as its a Buffalo Wireless router adapter, i.e. smarter than generic CN gear? The main lamp is likely a bit lower power rated than 25W figure I found on the web, unless the adapter limits power, possibly to prevent "router" damage? I'm hesitant to test the spotlight with a 12V adapter.

[sambul83]

Re: Converting Spotlight Power Supply

I wonder if this LED strip will do the job? Steel wire or plastic tube may be used to push it along the tunnel, unless uneven non-smooth cement walls prevent movement. I wonder if brightness 20-30LM at power 20W at 5m length of cold white strip is bright enough to lit the tunnel sufficiently well for video recording by a small cam without night vision? This is a costlier NeoFlex of German origin.

[Curious.George]

Re: Converting Spotlight Power Supply

What would be a good Spotlight to evenly lite up from one end a 5-10m 1.5x1.5 ft narrow square tunnel or pipe to take periodic short videos? The spotlight must entirely fit inside the tunnel. Ideally be flexible to insert it from a small angled pass, possibly through a small diameter side opening in the tunnel. Needed for sci-fi experiments.

"Evenly light up" is one of those delightfully non-technical phrases that means absolutely nothing! Radiation (of all wavelengths) drops off with distance so the intensity near the "emitter" will invariably be greater than at any distance from it. (i.e., an inverse square relationship)

Run a fluorescent tube down the exact center of that space for the most "even" lighting distribution. :-/

[sambul83]

Re: Converting Spotlight Power Supply

Q: How many posts does it take to light a light bulb?
A: We still don't know yet.

While people are willing to contribute good ideas to the topic, there is no reason for the thread to be finalized, even if the topic seems exhausted. In fact, this is one of threads where OP direct questions were in fact directly answered and the solution found, which is not always the case. Meaning its more useful than average for future readers.

What would be a good Spotlight to evenly lite up from one end a 5-10m 1.5x1.5 ft narrow square tunnel or pipe to take periodic short videos? The spotlight must entirely fit inside the tunnel. Ideally be flexible to insert it from a small angled pass, possibly through a small diameter side opening in the tunnel. Needed for sci-fi experiments.

[eccerr0r]

Re: Converting Spotlight Power Supply

Technically with 4x AA NiMH at 2Ah, it would still last 30+ minutes, alas not as bright as the 6V SLA pack...

If you hooked up a boost SMPS so that the 4xAA NiMHs could supply 25W constant power through that halogen lamp, then that single digit minutes is to be expected.

---

In case anyone's baffled by the above, this is the rebuttal: 5x AA NiMH low ESR 2Ah cells may be the best solution: it would last slightly longer in runtime than the original SLA pack and should be just as bright. Question is only the number of charge/discharge cycles it could take before conking out again. If you were able to design a overdischarge prevention circuit, this would be a viable solution...

[stj]

Re: Converting Spotlight Power Supply

well you could fit a shell with 4x AA nimh cells.
lifespan in min's (single digits)

[eccerr0r]

Re: Converting Spotlight Power Supply

Q: How many posts does it take to light a light bulb?
A: We still don't know yet.

[sambul83]

Re: Converting Spotlight Power Supply

add a capacitor ...

It balances out your previous suggestion to buy a new lamp.

[petehall347]

Re: Converting Spotlight Power Supply

how can taking 2 wires from an external power supply to a light bulb be so complicated ? add a capacitor ...

[Curious.George]

Re: Converting Spotlight Power Supply

Can you post a weblink to a similar booster to your "12VDC boost-converter brick" for laptop?

Attached pix of one of those devices (I have several different ones from different manufacturers with different capabilities) along with a view showing the two power inlets (AC & DC). The button on the far right enables "high power mode" (apparently, not to be used on aircraft) for rapid charging of laptop's battery. (The labels are just my way of keeping track of which "bits" belong to which "devices".)

Another pix shows one of the "spotlights" I've modified for use in and around the car (note short coiled cord). It's biggest claim to fame is not size but, rather, that it has a built-in PWM "dimmer" (control visible on the top side of the lamp) so I can use it under the hood of the car without blinding myself!

Last pic shows one of the portable power packs along with the "charger" that came with it, originally. Note that the charger SOURCES power through a "lighter plug" -- much the same way that the battery pack sources its stored power through that lighter socket! And, a "bare battery" to give you an idea of what lies inside.

[eccerr0r]

Re: Converting Spotlight Power Supply

On a similar note I have a handheld vacuum cleaner, same problem: batteries are toast. It uses three SubC NiCd batteries. The only PSU I have that will power it as-is without the batteries is my huge SCR bench PSU that can supply the amperes (with current limiting...)

I have an even worse problem in terms of powering it: the motor draws 30W or so steady state, peak instantaneous of 70W. Have yet to find some *inexpensive* Li-ion with a protection circuit that will let me draw 70W without shutting down... ha..

[petehall347]

Re: Converting Spotlight Power Supply

time is money . hey i save anything if deemed save able . one mans trash i suppose . sorry my pocket flash light is plenty good enough to light up large areas .. all i need is non fake batteries . fake ones have lasted 2 or 3 years though .

[sambul83]

Re: Converting Spotlight Power Supply

@ petehall347
Buying a "new nice modern lamp" would be too trivial thing to do, not exactly what this forum is about. The lamp is far not the only target in the budget hole .

@ Curious.George
With one project I need to evenly lit up a small tunnel compartment 1.5x1.5 ft about 5-10m (200-400 inches) through its length for 5min periodically. In another project, I need a small workspace 4x4m lit up at night for a few hours. One lamp may need to fit both tasks despite differences.

Can you post a weblink to a similar booster to your "12VDC boost-converter brick" for laptop?

[Curious.George]

Re: Converting Spotlight Power Supply

why not put the old lamp into retirement and buy a nice new modern one ?
i have had lots of them 10 million candle power things . they only last about 20 minutes and take a long time to recharge .

What's worse is the chargers can't be left unattended; they'll gleefully cook the battery if left on for too long.

or just get an external battery pack and use that . maybe get 2 packs so you get double time usage .

I rescued a couple of 12V packs from bits of portable medical equipment. They have a "lighter" socket wired to the battery (and very little else besides the case and carrying strap). The charger has a lighter plug that you would insert into the socket to recharge the battery.

I've put these in my bug-out-bags as a sort of "universal power pack". In that way, I can have equipment that can be powered from the car's "lighter" socket that will also work with this portable power pack (AM/FM/weather radios, CBs, spotlights, area lighting, etc. -- I even have a 12VDC boost-converter brick to power laptops at 19V)

I know I'll always have a fresh supply of charged batteries -- even if the portable pack is dead (cuz I can steal them from any of the UPSs, here)

[petehall347]

Re: Converting Spotlight Power Supply

why not put the old lamp into retirement and buy a nice new modern one ?
i have had lots of them 10 million candle power things . they only last about 20 minutes and take a long time to recharge .
or just get an external battery pack and use that . maybe get 2 packs so you get double time usage .