My new project in April SC

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For those interested in a sneak peek at my new little project coming up in
next months April issue of Silicon Chip.
http://www.alternatezone.com/electronics/ucurrent /

Just realised it's been almost 6 years since my last project in SC, how time
flies...

Dave.



Re: My new project in April SC
Looks useful.

The page doesn't give the overload specifications.

Was auto-off considered?


Bill


David L. Jones wrote:
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Re: My new project in April SC

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Auto-ranging would be nice too.....looks like a neat & useful bit of kit.

 



Re: My new project in April SC
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That was considered also, but again, the KISS principle won out.

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I'm betting that a lot of people won't have clue what it's actually useful
for! ;->
After all, all multimeters already have current ranges...
Hopefully the article will clear things up for them.

Dave.



Re: My new project in April SC
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In order to keep the burden voltage as low as possible (which is the whole
point of the project), overload protection has been ommited.

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Yes, I considered that in various ways, e.g. a small PIC with a smart
push-button power switch or by some other means, but went with the KISS
principle in the end. Some people groan when they see a micro in such
projects, I didn't want hate mail :->

Dave.



Re: My new project in April SC
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Fair enough, but in that case it would be useful for the user to know
the level of overload which is considered safe.

If you have implemented the device with current sense resistors and a
voltage amplifier then it might make sense to add protection for the
amplifier input to handle the case where a massive overload fuses the
current sense resistor.


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An optional auto-off feature might be a compromise.

Auto-off is of course a 'two-edged sword'.  I have a battery powered
differential probe at work and find that its auto turn off time is
usually too short for the way I work...  It's annoying, but probably
less so than continually replacing flat batteries.

Re: My new project in April SC
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That's what the ON-OFF switch is for of course, but that requires the mind
to be in gear also :->

Mine was going to be a "smart" auto-off. Not only uses a time period, but
senses input activity as well. i.e. no input current=no voltage=timeout
active. The ADC in a tiny 8 pin PIC could then serve both push-button power
switch and smart time-out duty.
But there were a few reasons I didn't go for that in the end.
You could even have an auto-on feature that briefly sampled the input every
second or whatever and switched on when input activity is sensed.
Perhaps in a more upmarket version.

Dave.



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