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Micro-Drive laser driver by rkcstr






Will the full range adjustable drivers have a 1 turn pot that goes through the full range? How sensitive will it be?

Thanks rckstr
 
should use these:
4272741.jpg

http://www.newark.com/bi-technologies-tt-electronics/43wr100lft7/trimmer/dp/15M2448

please let me know when you get them in stock.

i might need some help with my design LOL.
 
Yes, the pot is a single-turn and it is somewhat sensitive on the full-range due to the large range covered. But, it is the most demanded and most versatile. The lower half of the range is relatively simple to set and if you have patience and a light touch, you can set them to any current within a few mA anywhere within the entire range.

Also, I could use a lower value pot to get less sensitivity over the range, but the low end would be about 60mA vs 30mA. I don't know many people who still run diodes below that, but there may still be some who want to run a low current for a low power diode.

I would consider a multi-turn pot, but the cost is prohibitive. Sure, a couple dollars doesn't seem like much if you're building a few, but when you have a thousand drivers to build, that becomes a very significant cost. Plus, there aren't many multiturns which would be small enough... that one would probably be too tall and would make it not fit in an Aixiz module.
 
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I'm waiting to hear back from one of the assembly places to get a price from them. I sent the email Friday night, so I'm hoping he'll get back to me today sometime. If not, should be in the next day or so.

I have an idea of what the maximum cost will be, so I may end up starting the presale tomorrow or Wednesday just to get it started while I'm waiting to hear back.
 
Unforunately I won't have the time to set currents on the drivers. But, it is very simple to at least estimate the output by the method outlined in my instructions, which just involves measuring resistance (while it is not powered) across two points and calculating the current (or calculating the resistance you need for a current and setting it as close as possible). If you need accuracy (ie. if you're pushing limits of a diode), then using a method involving measuring actual output of the driver is better.

BTW, I will be working on updating and improving the instructions for all items. Some are really outdated and have inaccuracies, so I hope to improve that after I finish up my exam on June 15th.
 
I still don't know why using the ramp up method is not ever metioned.

Starting at a lower power and ramping it up till it is at its threshold then on up.

I could see it not the safest under power but a calm still hand could do it CIIW...:)
 
That would work fine, but a lot of the diodes we use today can have a safe operating current far beyond their threshold and without knowing the exact current you're pushing, you may overshoot into an unsafe range.

If you know a safe current range for the diode you intend to drive, then it's easier to just "set it and forget it" as [url="http://en.wikipedia.org/wiki/Ron_Popeil]Ron Popeil[/url] would say :D
 
I was told that I should have an estimate tomorrow from the place I was waiting on.

ALSO, I had a last minute idea, in relation to the idea of range sensitivity, where I could, with no extra parts (just a change of resistor and a little change in circuit paths), have a sort of selectable range on the driver, which would give better adjustability over the higher end, while also maintaining a lower current ability.

The idea is as follows: The standard configuration (how it is set from factory) will be a "low range" which puts out about 30 to 60mA. A higher range can be set by just soldering two pads on the board together, which would give ~60 to 430mA.

The other ranges that I offered before would still be possible as a kit, they would just have one less resistor to solder and the actual range would change a little (the low end would decrease).

So, what would YOU prefer? The idea above or the original "full range" driver?

EDIT: I just decided to go with the above idea with one modification. I figure most people will be using the higher range portion of driver, rather than 30-60mA range. So, there will still be bridging pads, but they will just come "pre-bridged" with a small trace connecting them. If you want to set a lower range, you simply break that trace (a pointed instrument will work just fine) and it can still be set to the high range again, if you want by soldering the two pads together.
 
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Sounds good. It seems that that idea is also the most versatile and easily changed. Flex drives require a little more effort and care in adjusting current levels. Any change in the estimate?
 
The changes should give a moderately improved adjustability in the upper range. It's still a single-turn pot and a relatively large range, so it will take a little work to set an exact current, but it will be a little easier. Also, the peak output goes up to about 440mA as well.

Anyway, I haven't heard back from the one guy yet. He said he should be able to get back to me today, but I guess that he wasn't able to. So, I hope that means tomorrow. But, I'm going to get the PCB manufacturing started, which will take at least a couple weeks, so there will be time in there to sort out the assembly. And, I'll go ahead and start up the pre-sale.

So, here's how prices will work:
- The prices listed in the pre-sale are 10% lower than the regular prices for the assembled drivers, when I get them, which reflects the pre-sale discount.
- BUT, LPF members will also get 10% off of the regular prices, which for the presale means you get 20% off of the regular prices. Don't forget to enter the discount code " LPF " during checkout to get your full discount!
- There are further discounts with larger amounts (quantities of 10-24, 25-49 and 50+).

And, the presale will go until June 23, 2009. I expect to have them in by approximately the end of the month (possibly earlier, possibly later, it's not definite yet). There will be plenty available, so feel free to buy as many as you want!
 
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Like I said in my last post, I'm hoping for the end of the month to get them in, but it may be a little longer. A good estimate will be approximately 3-5 weeks.

And, just to make sure it is clear: I am ordering a large amount of drivers to be assembled, so once these are in stock, they will be ready to ship at any time. Of course, they will be the regular price after the pre-sale. This pre-sale is just meant as an opportunity for those of you who were planning to buy some anyway to save a little money while also helping me fund the whole process (costs will be upwards of $4-5k!). So, 'thank you' to all of you who have or will be taking advantage of the pre-sale offer!
 
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