Hi Zach,
Maybe the impedance of your battery is causing your problem. :?:
The IC circuit is designed to be used with a Ni-Cad or Ni-MH battery that has an extremely low impedance. I think you are using a disposable battery whose impedance is much higher. The datasheet says to add ten low ESR 1000uF input capacitors to it if you measure it with a power supply instead of the recommended low impedance rechargeable battery. :lol:

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Uncle $crooge

 

If he used D cells, I don't think so. Even alkalines have a pretty impressive current capability. AA would probably do it for this current.

It wasn't designed for NiCd/NiMH- it says a "+3v" rail, not 2.4v. D cells would be an odd choice, rare in NiMH/NiCd on the consumer/surplus market.

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I thought what I'd do was I'd pretend I was one of those deaf-mutes.

 

Look at what Zetex says, and look at the huge difference in internal resistance of different battery types:

Attached Thumbnails

 

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Uncle $crooge

 

Wow that is a freaky design. I mean, 10x 1000uF is ludicrous, it takes up more space than another battery. If you had another battery you wouldn't even need a boost converter like this in the first place!

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I thought what I'd do was I'd pretend I was one of those deaf-mutes.

 

HOLY SMOKES!

I will try a rechargable battery with this circuit. If that is true, that REEALY sucks because I don't want to use rechargable batteries! They can't hold a charge over a long period of time.

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I'm no electronics god, i just talk too much.

 

It's hard to find a good D-cell rechargable battery.
The Ni-MH D-cell from Energizer is a big tin can with a little AA cell inside. They must be using awfully big wires in there because its internal resistance is only 11 milli-ohms. :lol:

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Uncle $crooge

 

I tried my NIMH batteries with the circuit, and the only noticable change was it got dimmer.

Something is turning on Q1 way too hard because its shorting VCC to ground. It should only be on to charge of L1, then turn off. Instead it is always on. I really want this circuit to work, but im so frustrated with it!

I guess I'll re-order the parts from farnell, and mount the SMT stuff on little circuitboards with wires so that I can experiment with this circuit on my breadboard.

One day it WILL work :evil:

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I'm no electronics god, i just talk too much.

 

Hi Zach,
I am sorry that changing the battery type didn't fix it.
I think the project's frequency would be too high and its output voltage would be too low (your syptoms?) if the value of the coil's and power transistor's 33milliohm current sensing resistor is too high.
How is its value marked?
How would you measure it?

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Uncle $crooge

 

I think ive finally got the bloody thing working!!

It is EXTREMELY bright with two regular AA batteries whose series voltage is only 1.35V!!

I ordered more of the SMT chips and transistors, made a PCB so that I could put them on my breadboard and fiddled around with it. I still don't know what was wrong with my PCB version.

I have one question though: This circuit is pulling 1.3A from those batteries. Only 100mA is going through the LED. Here's the weird thing: Around 1A is going through Q1and its getting very hot. Fortunately Q1 is rated at 4A.

Does this sound like a normal thing for a DC-DC converter or is there something wrong?

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I'm no electronics god, i just talk too much.

 

Hi Zach,
Yeah, something's wrong. Its efficiency is only about 20% when it should be better than 80%.
You have 1.35V at 1.3A from the battery which is 1.76W.
The LED is about 3.5V at only 100mA which is 0.35W.
0.35/1.76 = 20%. Therefore 80% of the battery's power is heating the circuit.

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Uncle $crooge

 

Yes, the same thing happened in my PCB circuit, Q1 was way overheating, passing at least 1A.

Do you have any suggestions as to what to try and do to solve this?

Im thrilled that I at least sort of got it working.

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I'm no electronics god, i just talk too much.

 

Hi Zach,
I'm stumped too unless you used a slow ordinary rectifier instead of the spec'd extremely fast-switching Schottky diode.
Also, if the core of the inductor saturates then it will act like just a piece of wire.

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Uncle $crooge

 

Hey audio, its definenately neither of those: The diode is one specified by the schematic, and the inductor is rated @ 3 amps, so its not saturating.

I havent got the chance to fiddle with it some more since i sort of got it working. I just got a digital camera so ill be able to post pics of the finished product when its done.

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I'm no electronics god, i just talk too much.

 

How many uH is your inductor?
If your inductor does not store enough energy, it may be trying to draw more current by leaving it on longer, yet the battery may peak out in the number of amps it will provide. It gets hot, sucks a lot of power, but little output.

You need an oscilloscope here, you can't get answers without it. For one, you need the current and voltage waveforms off the battery. Just the average that a multimeter gives won't help much.

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I thought what I'd do was I'd pretend I was one of those deaf-mutes.

 

I bought inductors for speaker cross-over networks from a high-end speaker manufacturer. They sounded bad. I measured them and their inductance was incorrect.
So I took my real-time-analyser into the manufacturer's showroom, played pink noise into their very expensive speakers and showed them the hole in the response cause by their incorrect inductors.
The high-end speaker manufacturer's quality control department cared so much about the appearance of their speakers that they didn't even measure them, maybe not even listen to them.

Zach, maybe the manufacturer of your inductor "hopes " it is 22uH and can pass 3A. :roll:

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Uncle $crooge