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Jonathan Hallameyer | 1 Apr 02:47
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Re: [EE] Back EMF and brushed DC motors.

Sean,
I was planning on using a phototransistor and LED to index the LED array
every time it went around on a rotation, and the method of pausing the PWM
would work pretty well when the rotor is on the back side of the clock, I
just wanted to see what I could do with brush noise for later robotics use.
I have a plan which I could get the clock working with, just gotta
overcomplicate it a bit and see if I can use that somewhere else.
-Jon

On 3/31/07, Sean Breheny <shb7 <at> cornell.edu> wrote:
>
> Hi Johnathan,
>
> If I understand your application properly, I would think that you need
> to know absolute position in the rotational cycle, not just roational
> speed. If that is truly what you need to know, then I don't see how
> you are going to get it from motor back EMF or noise from the brushes.
>
> I'd recommend using either an optical or magnetic sensor to give you a
> single pulse as the motor passes some rotational reference point. By
> counting the number of these pulses per second, you can get speed.
> Then, you can make an estimator which resets itself to 0 deg when it
> sees the pulse and then counts forward from there based on time and
> the latest best estimate of rotational speed.
>
> As for back EMF sensing, I have never tried it. For an application
> such as this, I think measuring speed would be very doable because
> torque will be a monotonic function of speed. This means that the
> current in the motor will increase as speed increases, so that the
> voltage across the motor terminals (which is the back EMF plus I*R),
(Continue reading)

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Vasile Surducan | 1 Apr 07:22
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Re: [EE]: MAX5061 Switching Regulator Controller

On 3/31/07, James Nick Sears <lists <at> jamesnsears.com> wrote:
> Thanks for the reply.  So the correct approach is simply to calculate
> the maximum resistance that leaves 7V at the input with the minimum
> supply voltage and the maximum current being drawn by the IC?

Sure.
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Vasile Surducan | 1 Apr 07:43
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Re: [EE]: High nit LCD's

AFIK US signed an agreement about using the international units system
with the beginning of 2007 so, the units for brightness is not the
nit.

http://en.wikipedia.org/wiki/Candela_per_square_metre

However, let's don't talk about religion&politics. :)
>From my experience (and I've saw many LCDs, most of them being
japanese products) there isn't any being able to display satisfactory
in full sun. Most of them will look like have been shutted down or the
backligt HV supply is dying.

The solution  is using a large view angle LCD and mask as much from
the sunlight with a sort of high bezels.

On 3/31/07, Dave King <KingDWS <at> shaw.ca> wrote:
> Just was reading the thread about case mods and looked up the source
> of the LCD screen the guy used. I noticed the prices of lcd's have
> dropped to the point where they are reasonable or about 1/10 of what
> they were when I first started working on my project. The high brightness
> or high nit lcd panels are about 3x the cost of the standard tft panels.
> My project requires visibility in sunlight.
>
> So here is the question...
>
> Would it be possible or has anyone taken a standard tft lcd panel and
> added high brightness side lighting (cft or led) and managed to make
> it work in bright sunlight? Or am I missing something on the differences
> of a standard lcd verses a high nit lcd?
>
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Robert Mann | 1 Apr 08:11

[OT] eBook Cover Design Software???

Anyone have any good experience with any eBook Cover Design Software.

The kind you would use to create software type box covers if you were
selling your software retail?
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wouter van ooijen | 1 Apr 09:25
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RE: [EE] Internship E

> BTW, this afternoon I was watching the 12PM news and I have 
> learned that 
> a company in the vibration sensors market, here in Switzerland, was 
> hiring and they have about 30 positions open. As their HR 
> manager said, 
> they are looking in EU and others countries 'cause there are 
> not enough 
> qualified people here.

Here in the Netherlands I too hear over and over that we do not have
enough well-educated people. Turkey is not EC yet, but maybe some
agreement already exists to make working here possible.

Wouter van Ooijen

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wouter van ooijen | 1 Apr 09:25
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RE: [EE] Internship E

> What he said. Olin is NOT representative of the majority of the list
> members, 

Maybe not, but he is in the USA and IIRC he has at least some influence
when his company hires people. So he might be more representative for
the group of people Yigit needs cooperation from that most other people
on the list. 

Wouter van Ooijen

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Ling SM | 1 Apr 11:12
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Re: [OT]your thoughts reliability analysis

> * I knew someone who did 217 calculations as his job.  One of the things 
> he did was help design color TV picture tubes so that they would fail a 
> couple of months after the 1 year warranty ran out.

Situations are even worse.

I have good reasons to suspect that my printer has an algo to 
intentionally killing itself and the print head.  I shall be able to do 
more test when my stock of refill ink run down.  For the time being, I 
shall resist to swap "old" print head to another "old" printer.

It is quite a tough money to make in the consumer electronics areana 
when compare to the fashion industry when a pair of jean easily price 
higher than a MP3 player.  But...

Ling SM
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Peter P. | 1 Apr 11:22
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[EE]: Over/undervoltage and ESD protection of new PICs (and other chips)


Since now most CMOS microprocessors are again sensitive to conduction of their
body diodes (as they were in CMOS CD4xxxA times), and are no longer immune to
body diode currents (as they were in CMOS CD4xxxB times, i.e. for 25 to 30
years), the time has come to look the problem in the face and find common
solutions, as I find that this 'return to the past' can be quite costly.

The problem is that many (most) CMOS chips are now specified for Vdd-0.3 to
Vcc+0.3 maximum limits *operating*. This means that:

a - body ESD diodes cannot be used for anything at all
b - internal MOSFET reverse diodes must be ignored
c - external clamps which are able to clamp at Vf=0.3V for usual surge currents
must be provided externally. Silicon clamps and tranzorbs do not work.
d - the cost of doing this must be assessed.
e - leakage from Schottky clamps compromises some of the advantages of CMOS
inputs. Its strong temperature dependence can make certain A/D schemes stop
working altogether (e.g. R/C a/d converter on external pin)

For a 13 IO pin part, this means that:

e - 26 diodes which were previously implied present are no longer present
f - the actual cost of the part is the cost of the part plus the cost of the
external suppressor plus the cost of the board space consumed, plus the cost of
extra routing (which can mean vias or a double sided board where one layer was
enough before).

The problem gets worse with more IO pins.

So according to my simple calculations, taking an 18-pin low cost PIC as example:
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Peter P. | 1 Apr 11:52
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Re: [OT] Fake components?

Jinx <joecolquitt <at> clear.net.nz> writes:

> Someone got busted in Auckland a few years ago selling RAM chips
> that were actually empty.

There used to be motherboards with 'cache' chips which were empty. You had to
look up the part numbers to find out. These were synchronous cache 'chips' gull
wing smd, large, soldered near the cpu.

I also got fake LM386 (oscillates at about 8 MHz in standard circuit) and fake
TDA2030 (oscillates at ~3 MHz).

Peter P.

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Dario Greggio | 1 Apr 12:24
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Re: [OT] Fake components?

Peter P. wrote:

> There used to be motherboards with 'cache' chips which were empty. You had to
> look up the part numbers to find out. These were synchronous cache 'chips' gull
> wing smd, large, soldered near the cpu.

Yeah, you're right!!
1993 maybe...

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Gmane