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FlexMod P3 Replacement?

Wolfman29

Wolfman29

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Hey everyone.

I was thinking that it's about time that a FlexMod replacement come about. I recently saw a thread where it was required, I thought that maybe it would be about time someone came up with a reasonable linear driver like the FlexMod. Then I figured, hey, why not me?

I'm just wondering, what kinds of things would you like to see in the... I dunno what we'll call it, BlitzMod? Hah. I plan on making it 3A capable and I want to keep it at or under $25 in price. I'd also like to get analog and TTL modulation as well, but I'd like some other suggestions!

EDIT: I have an idea of how I can do this based off of the BlitzLinear, but that would imply either continuous positive or a bigger voltage drop on the chip. Would you guys mind a continuously positive BlitzMod?
 
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ARG

ARG

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Suggestion? Open source :D I'd donate to the project.

Drivers come and go. If it were open source it wouldn't fade away.

<derp>
 
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Wolfman29

Wolfman29

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I would open source it if it didn't reveal my BlitzLinear's IC xD I know how much you love open source and I appreciate it too. And I'm getting tired of having to keep secrecy... but it's the only way I can manage to assure that I have reasonable income for school >.<

EDIT: And what do you mean, putting diodes in series is a pain? How would that mean you have to parallel several drivers? o.o Series diodes would imply low current, high voltage, not low voltage, high current.
 
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ARG

ARG

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Was trying to get across that more current would be nice for large diode arrays. :)

There's not much of a problem with secrecy IMO, if someone did copy your driver and use the same main IC they would be outed. Small community helps with this.

Hardly anyone DIY's their own drivers, so you wouldn't be losing sales; you'd probably pick up sales from the fact that it's open source :p

Just my opinion on it.
 
Wolfman29

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Alright, that's clearer XD

Anyway, I'll consider it. I'm currently working on a design that'll do 6A. How big was the FlexMod? I'll shoot to make it that big.
 
Wolfman29

Wolfman29

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Sorry for the double post, but I figured I had a lot to say here.

First and foremost, I'm not sure what the standard is on current ripple for the FlexMod. I don't know how it regulates. Second, what's the maximum frequency for TTL necessary? Anyone have this information? I've been looking into some standard, pre-built LED driver ICs, but most of them are boost and have a meh ripple. Linear drivers are also good, but they don't have a very fast response time. I'll continue to look into this.
 
djQUAN

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The flexmod appears to be a linear driver so it shouldn't have any ripple on the output.
 
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Things

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I've seen specs up to 20-30Khz quoted on proper lab modules. I believe the flexmod was actually capable of up to a few Mhz modulation.

You do not need any special chips special for this, you could do it on a dual opamp even.
 
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Wolfman29

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I realize that it can probably be done with an opamp + transistor circuit, but usually, using discretes (or close to it) lends to a higher part count and bigger part cost. I figured if I can find an IC that'll do the job, it would be better that way.

If I could get a board that can do 30KHz modulation, would that be sufficient?
 
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ElektroFreak

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1 MHz analog laser driver based on the LM317 or LM338 for up to 5A:

Sam's Laser FAQ - Diode Laser Power Supplies

This is looking promising in the simulations I've been running, in fact it works perfectly in simulations. I've got all the parts (not many really) just haven't etched the board yet. Very simple, very straightforward. I had considered the idea of modulating an LM317 myself a few years back but never pursued it.. turns out it's definitely doable.

ldschpcb.gif
 
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Wolfman29

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Hmm. Only problem is we don't want to have to use 3-4 LM317s. I suppose we could use an LM1085 or whatever. I guess this is open-source already! :D

Do we have analog on that?
 
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ElektroFreak

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Yep. Fully analog. Replacing the LM317 with an LM338 is a direct replacement and allows up to 5A current. No further modification required. You can even drop the 68pf and 10pF caps on the feedback loops of the op amp for slower speeds such as for show use. Also, use CA3240 op-amps instead of those shown if you're using the circuit for laser shows.

Applying a carefully controlled analog modulation signal coming from the op-amps to the adjust pin of the variable regulator causes the regulator to modulate its regulated output. There's one pot. At one end of the range the output is fully on, CW. As you sweep the pot's wiper, the signal becomes more and more modulated until it's all modulation. The ideal setting is almost all modulation, which leaves a tiny bias current running when the modulation is at 0V.

There's a very thorough explanation of the entire circuit in the Sam's FAQ link above that I highly recommend reading. It's really elegant how simple this is.
 
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Wolfman29

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Well, there we go! :D Someone should make these. Or something. I take it this is known on PL?
 
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ElektroFreak

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I'm getting ready to build a prototype for myself currently, although I've been dragging ass due to some other obligations. Really I just need to etch and drill the board and solder the parts on. If we could get the blank boards produced in bulk it would be that much easier for people, but I think that the creator of the circuit stated their opposition to the idea of commercializing it, so selling the boards for profit might be an issue.
 
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