SatCure--LS-- Night light

[KenBar]

I wanted an easier SatCure circuit that someone could build without doing knat surgery.

Hosfelt has dirt cheap "FP" cores and 2N3904 transistors.

I tried 1, then 2, then 3 cores to see how closely I could get to the original circuit. I used a high efficiency transistor as well for the "standard".

What I came up with was 2 of the cheap FP ( this is the part number) cores will give you the greatest efficiency very close to the original and only a little larger. The overall current consumption was almost the same for all 3 BUT by using 2, you could get greater current through the LS. ( Saturation??)


Using 2 cores and 20-25 windings, I am running this at overall 2.72 ma and 1ma through the amber LS.

The wire I used is just a hair under the thickness of an index card...MUCH MUCH easier to work with.

I do not have a way to measure output SO I used a comparative method.

I used a Pal Gold as standard, index cards as the measure.

This "sat cure" circuit, drawing overall 2.72ma on ONE C CELL, will "punch through 5 index cards.

A pal gold on low will punch through 5.5.

It is a fairly bright night light drawing zip for power.

This was using a 47K resistor.

 

[Steelwolf]

2.72mA? Or is that supposed to be 2.72A? 2.72mA is really very little. Not even enough to start a Nichia glowing.

But you already know that.

 

[KenBar]

It is milliamps.

Next to nothing.
Underneath the cover of the light is one C cell battery....

This is a night light keep in mind. HOWEVER it is does punch through as much as a Pal Gold on dim.

I put a volt meter on it and it registered 1.7 volts... I also think that this is the "average" due to the circuit as the LS specs are 2.25 to 4 volts.

The main thing is ... it runs a LONG time on a C cell as the Satcure still pumps out at .8 volts I think.

I had it on a bread board for a week and the battery still was over 1.5 volts...barely

I did an overkill on the heat sink as I was not sure if I wanted to drive it hard. The metal plate on which the heat sink sits keeps the heat from "coloring" the plastic box.

 

[jeff1500]

I'd like to try to build a SatCure type circuit like this one, but I'm having trouble figuring out what parts to buy. The guy at the electronics store didn't recognize the numbers on the schematic. He says I need to find manufacturer's cross reference numbers. I can't seem to figure out how. Any ideas?

Can I run two white led's off this circuit? Will it be dim?

 

[jeff1500]

P.S. How do you wind your transformer cores? Is one set of windings on one side and the second set on the other, or can they overlap one another?

 

[KenBar]

Probably the easiest way to do it is order a kit from England.
"Micro-Mini Torch kit"

Where to get original Kit from London. It has all the instructions etc. Then, start substituting parts till you get what you want.
Here is a thread earlier that has info. you might could use..
SatCure Tips

Transistors that I have successfully used are:
ZTX650 ( fairly expensive...did not give that much greater results.
2N3904
MPS3904
MPS2222A
-------------
If space is not extremely important, use the cores in the post above...MUCH easied to wind. I can make one totally in under 5 min. My first one took over 2 hours.
Here is what the ones I make now look like...

 

[Bart]

OK this is new to me... what is a SatCure circuit and what does it do?

 

[jeff1500]

3.6 volts to run a white led is kind of awkward to get and package. Three Nimh batteries is 1.2v x 3 = 3.6 v or you can use a resistor to drop down 3, 1.5 volt batteries.

There's a nice $20. electronic circuit board with an IC from National Semiconductor (LM2621 evaluation kit) that you can change the feed back resistor on to get a very stable 3.6 volts from two cells. It's small so a steady hand is required to do the soldering.

SatCure is an English kit company. They sell the above circuit minus the diode and capacitor that will step up the voltage from a single battery enough to run a white led. It's fairly expensive as I recall, and I'm not sure if it will give full led brightness.

I like my 2AA light and I want a way to make it work with an led or two. If I can substitute this circuit for one of the batteries the led will lite.

I found the above circuit on an electonics website authored by someone who looks to be very expert, so I want to try his circuit to see how bright it is. He's in Japan.

In the process, I'm trying to learn the language of our local electronics store.

So far, maybe the transistor is mfg part no. 2sc3279, ECG part no. 11, NTE11, NPN, Bipolar, Si, 10v, 2a, .75 w, 150 mHz, TO-92 package

Schottky diode, Vishay Telefunken BAT81S, ECG 585, DO-35 package

The transformer core: Maybe OD=8mm, ID=4.5mm, L=4mm

1/2 watt for the 1k ohm resistor sounds like plenty. 0.020 amps * 3.6 volts = .072 watts if all the current for one led went through the resistor, which it doesn't, so 1/4 or 1/8 watt sounds better.

Capacitor, polarized, 47uF, aluminum electrolytic, radial, long lead is positive

1. What happens if there are two white leds in the circuit?

2. Is there a way to use two transistors?

3. How do you calculate the led voltage or current based on the circuit diagram?

4. Can you make your own transformer coil out of a stack of steel washers? Does it matter which way the windings are wrapped? The square dots on the transformer symbol mark the phase relationship. They're on opposite sides.

Right hand rule says wrap your fingers in the direction of winding and magnetic flux goes in the direction of your thumb, so probably the square dot is the flux direction.

 

[jeff1500]

KenBar,

What wire gauge size or diameter are you using for the transformer?

 

[KenBar]

Size wire... Sorry.. I don't know.
Look at the picture at the top and compare it to the width of the line on the index card. I don't think it is critical. Gadget has some he sent me that is "hair fine" and worked great except it was very easy to break. I ordered a spool from London ( SatCure) for 5 bucks that was a little thicker. I could not find the invoice.

I try to get 20 turns around the core and fill it up. If I am using a bigger core, I use a slightly bigger wire...stuff I have in a heap of torn apart things....speaker cones, shake flashlights etc

Perhaps Gadget can tell you the exact size.
The circuit seems pretty flexible.

 

[jeff1500]

I found this in the archive:

The wire is 38SWG or 0.0060". I don't know what this is in AWG but I'm sure you can find out. The stuff I use is polyurethane coated. You need a 90cm length. That's a yard. You fold it in half and thread the folded end through the bead until only two 1.5 inch tails remain. Then thread the folded end through the bead another 19 to 20 times. Finally, snip the folded end so you have four wires. Measure them for continuity so you can pair them and solder two non-connected ends together. Take care when you "tin" the ends because the urethane gives off poisonous fumes.

oh one more thing which should help- if you have a favourite electronic components supplier nearby, or a catalogue for a mailorder firm, look for a tubular ferrite bead (may be described as an "anti parisitic bead") with the following dimentions-

Length, 5mm. outer diameter 4mm, inner hole 1.8mm. These measurements are approximate, one within +/- 0.1mm should do fine.

And it looks like more than one led can be put in series.

Ya, like you said, sounds like a pretty flexible circuit.

 

[Nick]

This might be of some help.
.0060"=34 AWG
36SWG=.0076"=32 AWG
so you need 32-34 AWG wire and i guess the "hair thin" wire is around 38 AWG?

you can buy wire here, but i dont know if they are reputable.