9v clip-on flashlight

I've been using these cheap flashlight "heads" that clip on to
a 9v battery. Pretty simple, switch, resistor and one 5mm LED.
They provide a small but respectable amount of light. They can
be fed by a supply of batteries taken from smoke detectors etc.
typically still at 7-8v, and run down to about 3.5v where they
become too dim to be much use. Even zinc-carbons can have
decent after-life (before proper disposal).

I found these at a discount store initially 3 for $5, then $2, but
were cleared out and have not seen them since, anywhere locally.

Conversion is simple but not very efficient. Can someone
point to a simple buck convertor circuit that would step down
say 4-10v to drive a LED at 10-15mA? Simplicity, efficiency,
and ease of part availability are important factors.

Dave

there was a DIY thread a while ago where someone made a direct drive light using a 9V battery. it was pretty slick, and used common parts from radio hack IIRC.

I like the Safelight idea better. It completely encloses the 9v battery. I think it is at least water resistant. I have several and use them for night lights in standby or low mode.

The Safe-Light Handyman LED Flashlight

Pak-lites were once cheap to come by, nowadays they run nearly $20 :green:
its basically just a plastic cap, a 9V connector, two LEDs in series, and a STDP toggle with two different value resistors:candle:

Yes, I know. Here in Boulder Safelites are $15 while Pak-lites are $26 last time I looked. Pretty screwy situation if you as me.

I picked up a sunbeam red led 9v light and swapped out the red led for a white one. the 100 ohm resistor in it worked fine for used 9v batteries to limit current and it runs forever off of smoke detector and answering machine battery pulls. The had them a dollar tree awhile back. Personally I don't see paying more than $20 for a 5mm led based flashlight you can spend half that on more 9v batteries and buy a 5mm based AA or AAA light instead.

Light Sabre said:

Yes, I know. Here in Boulder Safelites are $15 while Pak-lites are $26 last time I looked. Pretty screwy situation if you as me.

Click to expand...

can you believe two years ago Pak-lites were $8 shipped from lighthound?:candle:

Illum said:

can you believe two years ago Pak-lites were $8 shipped from lighthound?:candle:

Click to expand...

that would be a decent price, for $26 they should have a rebel or cree emitter in them a decent bin at that IMO.

Illum said:

Pak-lites were once cheap to come by, nowadays they run nearly $30 :green:
its basically just a plastic cap, a 9V connector, two LEDs in series, and a STDP toggle with two different value resistors:candle:

Click to expand...

Just checked lighthound, Prices not near $30 there.
http://www.lighthound.com/search.asp?keyword=pak-lite&search=GO

think2x said:

Just checked lighthound, Prices not near $30 there.
http://www.lighthound.com/search.asp?keyword=pak-lite&search=GO

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hmm...you are right, wonder where that information came from:thinking:

Some time ago I bought three Safe Lite of three different colour for my collection and possibly for some real world use. I also bought some hard-to-find 500 mAh 9 V Li-Ion rechargeable batteries for them.
I was put off from their circuit design. While I like the rubberised casing and the multi mode level switch, and the possibility of years-long glowing, I realised that there is no actual power conversion in the circuit; in any of the brightness levels, two-thirds of the power drawn from the 9 V battery are wasted as heat.
I didn't liked this, since in my opinion it defeats the use of relatively high voltage battery, so they are stored in a box now.

Anthony

Interestingly, Lighthound actually stocks 2 version - approx $ 10 and $ 20.

Harry

If anyone's interested I found some 9V night light type lights at the Dollar Tree awhile back and they probably still have some left. They are not very bright, but they are kind of neat and work well. You stand them up and they turn on, set them on the side and they turn off. They are red and I have a nearly dead 9v battery in it that registers under 4v and it works fine still.

ampdude said:

If anyone's interested I found some 9V night light type lights at the Dollar Tree awhile back and they probably still have some left. They are not very bright, but they are kind of neat and work well. You stand them up and they turn on, set them on the side and they turn off. They are red and I have a nearly dead 9v battery in it that registers under 4v and it works fine still.

Click to expand...

I have one and replaced the red led with a white one, it runs fine off of used dead 9v batteries with the 100 ohm resistor in it.

Ray_of_Light said:

Some time ago I bought three Safe Lite of three different colour for my collection and possibly for some real world use. I also bought some hard-to-find 500 mAh 9 V Li-Ion rechargeable batteries for them.
I was put off from their circuit design. While I like the rubberised casing and the multi mode level switch, and the possibility of years-long glowing, I realised that there is no actual power conversion in the circuit; in any of the brightness levels, two-thirds of the power drawn from the 9 V battery are wasted as heat.
I didn't liked this, since in my opinion it defeats the use of relatively high voltage battery, so they are stored in a box now.

Anthony

Click to expand...

I don't believe that's the case at all about wasting power. The ones I have use PWM on low, can tell by the PWM noise on my AM radio. No other mode uses PWM. The nightlight/locator glow does intead last a year or two. It can be turned off if you don't need it. Every flashlight with a buck or boost regulator "wastes", if you want to call it that, a little power in order for the flashlight to run at all. I use 2 of mine on low for a night light in my bedroom every night for several weeks with 9V batteries that won't power anything else


HarryN: The reason that there 2 version and with that price difference is that there is a civilian version and a military version of the Safelight. The military version is somewhat different in the way it works compared to the other one.

Dave_H said:

I've been using these cheap flashlight "heads" that clip on to
a 9v battery. Pretty simple, switch, resistor and one 5mm LED....
Conversion is simple but not very efficient. Can someone
point to a simple buck convertor circuit that would step down
say 4-10v to drive a LED at 10-15mA? Simplicity, efficiency,
and ease of part availability are important factors.

Dave

Click to expand...

That doesn't make much sense. Normally you'd just use a resistor and two leds in series, 3.5 volts or so drop across each led, so you get 2x the output and don't need any regulation. Works great.

Mine, on high, draws about 40 mA from the 9 V battery. I measure the same current in series with the LED.
There is no hint of PWM on high, as you said. As the battery runs dry, the current decreases. It seems to me that, in series with the LED, there is a drop resistor and an electronic switch. When I said "wasted", I wasn't referring to the normal inefficiencies of a switching or PWM regulator, but to the use of a drop resistor in the circuit.
If a buck or PWM regulator were used on high brightness instead, the power consumption would have been aroung 10 mA at 9 V, instead of 40 mA, while keeping the same brightness.

Anthony