OFF TOPIC: charging the capacitor

[jBeam]

This is one of those exotic questions and I'm sorry if this is not something for this forum.

Hardware:
DC source ( 1,5V~10mA )
16F877 MCU
100V capasitor

What i want to do:
I'm studying capacitor charging process and flash part of my "old" camera.
Basically, i want to make the same electronics, (mainly, charging the capacitor ) with use of 16F877. Main thing is to reduce the electronics and to get the same charging effect. Is this possible thru MCU and less electronics ?

[C Turner]

Well, first off, 1.5 volts isn't enough to run a PIC by itself: One would need a circuit to generate enough voltage to operate a PIC - and this isn't a likely proposition if you are trying to build something that will run for a long time on batteries.

Also, a PIC16F877 is likely to be gross overkill for about anything that you'd be doing with a photoflash: An 8-pin device would likely be more appropriate.

Comment: I've noted that some PICs will run below 1.5 volts, but don't count on it! Also, remember that 1.5 volt cells only put out 1.5 volts when they are fresh - they rapidly drop down in voltage and still have approximately half of their life left when they are down to 1.2-1.3 volts.

Secondly, 100 volts is likely to be way too low to run about any photoflash that you run across: Even small tubes aren't likely to be happy much below 200 volts, and 300 volts is about right - but that's assuming that your goal is to make it flash: If it's just 100 volts of DC that you are after (but at practically no current) then that's another story.

Anway, completely ignoring the fact that a PIC won't run directly from 1.5 volts, you have a few options:

- A capacitor voltage multiplier. Theoretically, the I/O pin of a PIC could directly do this, but it would take a VERY long time to charge - if you had a reasonable-sized capacitor, it would be quite inefficient, and it would require a LOT of parts. Practically speaking, you would NEVER do it this way.

- Use the the PIC to drive a transistor-based transformer-output voltage converter. This could work - provided that you got the right transformer...

- Use the flash unit from a single-use camera. This is by far the best approach, as you could buy a disposable camera with flash for cheap (I've seen them on clearance for $2US frequently) and simply throw away the film - and they are often found for cheap at surplus outlets. These already contain a complete, ready-to-go flash unit. Note that these units typically pull about an amp when starting up, dropping to a 100-200 mA by the time the capacitor is charged, and that they generate the about 300 volts - which is potentially lethal!

Now, if you want to have the PIC do things like turn on the flash unit to charge the capacitor and make it flash (assuming that you are interested in making it flash, rather than just generate voltage) you have to do come up with all sorts of other interface circuitry - but that's something else...

Good luck,

CT

[Sigma EE]

Looks like he's trying to reinvent the wheel into a square one.

[rnielsen]

[Humberto]

JBeam, yes this is OT.

C Turner shows you all the possibilities to start working with your project and
Ronald made a good and constructive comment with:

[SherpaDoug]

[Humberto]

Hi SherpaDoug,

Logic exercise:

You are telling us about your EX boss, hence: you already do not work with him.
If you do not work with him I can propose the following statement:

[jecottrell]

....now that this train is off the tracks, I'll jump aboard.

My motto is:

"Why by something for $50 when you can make it yourself with $200 of materials and $1000 worth of tools?"

Don't laugh, I actually convinced my wife it would be better to by a shop full of tools and build our furniture than by the crap from the stores. Worked great, got really nice looking furniture after some hard work and a pretty nice shop to boot.

I dread the day when one of the kids needs brain surgery and I have to do that myself! (There's probably some psych term for the affliction...)

[SherpaDoug]

Humberto,
Unfortunately it was me who was dismissed, not the boss. Now the boss is the only one in the department who has been with the company for more than a year.

Jecottrell,
You have left out the important factor of time. You can buy it for $50 in an hour. But making it will take weeks!
_________________
The search for better is endless. Instead simply find very good and get the job done.

[Humberto]

SherpaDoug, my apologies to you. I hope you were not offended with this,
we have tried only to see the things with a little humour...

Now I want to know:(just curious...)
- how hard is to be unemployed in USA, I mean do you receive a Social Security
help while not working ?
- how long did you had been finding a new job until you got it?

Best wishes,

Humberto

[SherpaDoug]

No offence was taken. I am not an easy person to offend anyway.

But since you asked... In 2002 the company I was working for, Imetrix went bankrupt. We built a robot that crawls underwater on the hull of a ship and inspects it for rust, cracks, dents, etc. Over a period of months as Imetrix went under most of us started working part time as work and funds dwindled. During that time I started working for my next company Benthos. When Imetrix failed for good I started working full time for Benthos, at a much higher sallary than at Imetrix.

But company morale was bad at Benthos and few employees stayed very long. I worked on a bleeding edge sonar project that they had spent too much money on to allow it to fail. Fortunately I was also working on their line of underwater robots which was fun and successful so I was not completely demoralized.

I was surprised when I was fired in July 2005. I thought my boss was going to be the one to go instead of me. I started collecting unemployment payments, about 1/3 of my previous pay, and let people know I was looking for work.

A couple of months later I heard from SMS, who was one of the biggest customers of Imetrix and who bought the Imetrix assets in the bankruptcy. They are still running the Imetrix robot but after three years they were running out of spare parts and wanted to make some improvements. They asked if I was interested in helping them. Unfortunately they are based in Virginia, about 10 hours drive away and I didn't want to move. They had actually offered me a job in 2002 if I was willing to move to Virginia. So for the last year I have been an "Independent Consultant" with SMS as my sole (paying) client. It pays less than even when I was working at Imetrix, but it is enough and gives me lots of time to work on projects of my own. I am now working on an improved way for the crawlers to navigate on the bottom of a ship. If it works and SMS likes it they may buy it. Or I can try to sell it to someone else. At the very least it is a fun project.

So I was only unemployed for about three months. I am still looking for more work but I have enough to get by and I am oh so glad to be out of Benthos!
_________________
The search for better is endless. Instead simply find very good and get the job done.

[dbotkin]

[Douglas Kennedy]

It will often be true that if the only criteria is cost or looks; that buying rather than building is the way to go. You can rationalize the added cost of DIY by the fact that a new tool shows up in your garage but many feel the point of DIY is in that it is frequently a fun way to learn.

[Humberto]

This thread turn out to be most interesting...

JBeam wrote:

[dbotkin]