For those interested in a sneak peek at my new little project coming up in next months April issue of Silicon Chip.
Just realised it's been almost 6 years since my last project in SC, how time flies...
Dave.
Looks useful.
The page doesn't give the overload specifications.
Was auto-off considered?
Bill
David L. J> For those interested in a sneak peek at my new little project coming up in
Auto-ranging would be nice too.....looks like a neat & useful bit of kit.
In order to keep the burden voltage as low as possible (which is the whole point of the project), overload protection has been ommited.
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.
That was considered also, but again, the KISS principle won out.
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.
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.
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.
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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