Pulse skipping regulated SatCure version

[KenBar]

Martin in Manchester, England, ( aka SatCure ) just sent this to me.

I have been looking for this concept for some time....perhaps it was posted elsewhere?
If so, it was not in a format that I could understand...

This looks quite simple and uses the "hand wound bead" which is also what I was wanting.

Anyone interested in building it? I am starting to look for parts.

I have one question.

I found several transistors that work for the original circuit.
Some were real easy to find...others were hard. They all worked quite well.

Is there a "transistor source" like Hosfelt that would list "swappable parts" ?

I want to build the first one as close to this as I can...and then start substituting.


Picture.. ( I put link as it was too big) KenBar

 

[Mike]

Kenbar,

Why are you interested in using this pulse skipping circuit? That is a lot more work than the circuit on the left...with what benefit for LEDs?

 

[Steelwolf]

The pulse skipping circuit seems to be more work than what is necessary. LEDs, unless you over-power them and generate a thermal runaway, can be considered a constant load. The circuit on the left looks similar to the circuit that I think Gadget(?) was advocating, except that he didn't have that extra capacitor parallel to the battery.

For those capacitors, what is their rated voltage?

Or more importantly, how do I determine the capacitor size I am supposed to use (in general/other applications)? ie, **** Smith's supplies capacitors of varying capacitance, but they almost always seem to be 6.3V, 10V, 16V, 23V and 50V. The first 3 seem to be prevalent in the tantalum type caps, electrolytics start from 16V up. How important is the rated voltage, especially in the smaller caps? Maybe I should start another thread for this?

 

[Go Go Gadget Flashlight]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Steelwolf:
... The circuit on the left looks similar to the circuit that I think Gadget(?) was advocating, except that he didn't have that extra capacitor parallel to the battery.<HR></BLOCKQUOTE>

Yep, that's the article the circuit came from.

KenBar, didn't I email that to you about a month ago?

According to the article, if you have a fairly contant load, the left circuit is the one to use. I don't think the one on the right puts out any more power, just controls it better so it doesn't skyrocket with no load. Remember, the basic Satcure circuit hits about 50v with no load.

Steelwolf, I think all the caps in the left circuit are 16v electrolytics.

 

[Coherence]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR> how do I determine the capacitor size I am supposed to use (in general/other applications)?<HR></BLOCKQUOTE>

Simple (I think): the capacitor should be rated to handle any voltage the circuit could present to it.

Figuring out that number is the hard part.

For fig. 1 A:

C1 should rate at least the battery voltage.

C2 should rate 30 volts minimum if you ever leave the output as an open circuit. Otherwise, it should rate the maximum voltage drop across the load (whatever is connected to the output).

What is the maximum voltage drop across the load? Well, what is the load? Let's say 1 single white LED.

What is the voltage drop? 3.6v?

It depends. If you drive it with a constant 20ma then 3.6 volts is right. The above circuit and the SatCure circuit don't work that way.

I think C2 is there just to smooth the output and the diode is just so C2 doesn't interfere during the charging cycle of the coil. You can drop both for a LED load (the charge/discharge cycle is far too rapid for your eyes to see, so fluctuations don't matter, you see an 'average'). By the same token, C1 is just to smooth the input voltage, a battery presumably, you can drop it for any battery that can handle the demand on it during the charge cycle (anything bigger than button cells I guess).

So you are left with the SatCure circuit in other words.

 

[KenBar]

Gadget, I think you are right.

You sent me some stuff you asked that I not post...then my computer blew up ( thanks to WindowsME

and my Ghosted image did not have it. That must have been it!

Well this was sort of a disappointment. I guess I let "Tim the Toolman" get the best of me. I assumed more was better. No need to complicate things if not needed. I can do a SatCure from start to finish in 15 min now.

I was going to make a flashlight that had multiple buttons that selected different combos of lights and assumed this would do the trick... It looks like multiple SatCure "classics" would be the best if I needed more power.

Besides....I really don't want to build anymore except the basic SatCure since Grandsee is going to make his module available. I really am looking forward to it.
He feels it will not be a seller...??? I guess that would depend on rounding up the target market. I can see it blister packed.....well...whatever. You never know. 15 years ago they made great fun of us on the "other" side of the hallway....lowly pc people against main frame sophisticates. We took sales from 3 million a year to over 40 in 4 years and then they were allout of jobs. However, 2 years ago everything went belly up. Crazy world.... That's why I grow dental floss now.

 

[Steelwolf]

So, I can use capacitors of any rated voltage so long as it exceeds the expected voltage that might be delivered to it?

In the case of this circuit, would there be any noticeable reduction in performance if I used a 50V cap to smooth the output as opposed to say a 10V cap (which more closely matches the LED voltage drop)?

 

[Coherence]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR> So, I can use capacitors of any rated voltage so long as it exceeds the expected voltage that might be delivered to it? <HR></BLOCKQUOTE>

Yes.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
In the case of this circuit, would there be any noticeable reduction in performance if I used a 50V cap to smooth the output as opposed to say a 10V cap (which more closely matches the LED voltage drop)?
<HR></BLOCKQUOTE>

No, if anything it will help, not hurt.

Someone correct me if this is wrong?

 

[Go Go Gadget Flashlight]

Coherence has it.

As long as the cap is rated at or above the voltage it might see, you'll be fine.

As for the voltage, I think the best this circuit might do is 2 LEDs in series. So, anything over 7 volts is overkill. Won't hurt anything, but the higher the voltage, the bigger the cap (for he same capacity).
As long as you don't run the circuit without the LED as a load...

 

[Go Go Gadget Flashlight]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by KenBar:
...Well this was sort of a disappointment. I guess I let "Tim the Toolman" get the best of me. I assumed more was better. No need to complicate things if not needed. I can do a SatCure from start to finish in 15 min now...<HR></BLOCKQUOTE>

Yep. We had our fun, but the Satcure circuit just isn't beefy enough or efficient enough for really good light output.

I'll be very interested to see how much Peter will have to charge for the modules. From a manufacturer's standpoint, little batches cost more to make than big ones. Setup costs have to be absorbed by the whole run and a little run means more "setup cost" per unit.

Don't get me wrong, I'll be wanting at least one of each type as soon as they're available!

 

[Steelwolf]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR> I'll be very interested to see how much Peter will have to charge for the modules. From a manufacturer's standpoint, little batches cost more to make than big ones. Setup costs have to be absorbed by the whole run and a little run means more "setup cost" per unit.<HR></BLOCKQUOTE> But it is not really a small batch as such. Just that he produces the circuit boards as he normally does, but instead of assembling it in to the head, just embalm it in epoxy with the leads sticking out.

 

[Mike]

Gadget,

Using the modified Satcure circuit (with diode and cap) and 2 AAA batteries (3V) as an input I was able to push 14mA through 3 white LEDs in series.

 

[Go Go Gadget Flashlight]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Mike:
Gadget,

Using the modified Satcure circuit (with diode and cap) and 2 AAA batteries (3V) as an input I was able to push 14mA through 3 white LEDs in series.<HR></BLOCKQUOTE>


That's pretty good. What current does it put through only 2 LEDs?

 

[Mike]

I believe it was about 22mA with 2 LEDs in series. I can't check now since I've mounted that circuit in a battery holder.