I was reading the datasheet on my ATTiny13, and noticed the following
ABSOLUTE MAXIMUM ratings:

Maximum Operating Voltage 6.0V
DC Current Vcc and GND pins:  200 mA

I was planning on powering my device with 4 1.2 NiMH batteries.  Do I
still need a 78L05 voltage regulator, or can I skip that?  (I've got
one just in case, but wondering if it's necessary with 4.8V
nominal...)

Why the restriction on the DC current input?  Won't the device just
suck as much current as it needs?  Or should I put a resistor there in
series with Vcc...?  R=V/I = 5.0V / 0.2A = 25 ohms?

Thanks,

Michael

m...@gmail.com wrote:

> I was reading the datasheet on my ATTiny13, and noticed the following
> ABSOLUTE MAXIMUM ratings:
>
> Maximum Operating Voltage 6.0V
> DC Current Vcc and GND pins:  200 mA
>
> I was planning on powering my device with 4 1.2 NiMH batteries.  Do I
> still need a 78L05 voltage regulator, or can I skip that?  (I've got
> one just in case, but wondering if it's necessary with 4.8V
> nominal...)

It should be just fine.


> Why the restriction on the DC current input?  Won't the device just
> suck as much current as it needs?  Or should I put a resistor there in
> series with Vcc...?  R=V/I = 5.0V / 0.2A = 25 ohms?

Eh ?

It means you can't exceed that current on those pins *including any load
currents*.

Graham

m...@gmail.com wrote:
> I was reading the datasheet on my ATTiny13, and noticed the following
> ABSOLUTE MAXIMUM ratings:
> 
> Maximum Operating Voltage 6.0V
> DC Current Vcc and GND pins:  200 mA
> 
> I was planning on powering my device with 4 1.2 NiMH batteries.  Do I
> still need a 78L05 voltage regulator, or can I skip that?  (I've got
> one just in case, but wondering if it's necessary with 4.8V
> nominal...)
> 
> Why the restriction on the DC current input?  Won't the device just
> suck as much current as it needs?  Or should I put a resistor there in
> series with Vcc...?  R=V/I = 5.0V / 0.2A = 25 ohms?
> 
NiMH batteries will routinely show 1.25V/cell when they are fully 
charged, which puts you right at 6V.  1.3V/cell is not unheard of, and 
that puts you over.  I'd recommend a low drop out* 5V regulator.  Even 
if you could just go straight off the battery you want to have some 
healthy capacitance on the power supply line, as batteries have 
significant internal resistance that can cause supply-line droop, which 
messes up the processor.

The DC current input restriction is there because something in the chip 
will burn up if you exceed it.  The chip by itself shouldn't consume 
much power (the amount will be in the data sheet), but you will be 
driving things from it's output pins -- the maximum current directive is 
to you, the circuit designer, to make sure you don't hang too many 
things off of the chip.

*  The 78L05 needs more than 1.5V of overhead, depending on whose you 
buy and how much current you pull -- I figure that 8V into the regulator 
is the minimum safe value, and I prefer 9V.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

On Jul 3, 9:17 am, Tim Wescott <t...@seemywebsite.com> wrote:
> mrdarr...@gmail.com wrote:
> > I was reading the datasheet on my ATTiny13, and noticed the following
> > ABSOLUTE MAXIMUM ratings:
>
> > Maximum Operating Voltage 6.0V
> > DC Current Vcc and GND pins:  200 mA
>
> > I was planning on powering my device with 4 1.2 NiMH batteries.  Do I
> > still need a 78L05 voltage regulator, or can I skip that?  (I've got
> > one just in case, but wondering if it's necessary with 4.8V
> > nominal...)
>
> > Why the restriction on the DC current input?  Won't the device just
> > suck as much current as it needs?  Or should I put a resistor there in
> > series with Vcc...?  R=V/I = 5.0V / 0.2A = 25 ohms?
>
> NiMH batteries will routinely show 1.25V/cell when they are fully
> charged, which puts you right at 6V.  1.3V/cell is not unheard of, and
> that puts you over.  I'd recommend a low drop out* 5V regulator.  Even
> if you could just go straight off the battery you want to have some
> healthy capacitance on the power supply line, as batteries have
> significant internal resistance that can cause supply-line droop, which
> messes up the processor.
>
> The DC current input restriction is there because something in the chip
> will burn up if you exceed it.  The chip by itself shouldn't consume
> much power (the amount will be in the data sheet), but you will be
> driving things from it's output pins -- the maximum current directive is
> to you, the circuit designer, to make sure you don't hang too many
> things off of the chip.
>
> *  The 78L05 needs more than 1.5V of overhead, depending on whose you
> buy and how much current you pull -- I figure that 8V into the regulator
> is the minimum safe value, and I prefer 9V.
>
> --
>
> Tim Wescott
> Wescott Design Serviceshttp://www.wescottdesign.com
>
> Do you need to implement control loops in software?
> "Applied Control Theory for Embedded Systems" gives you just what it says.
> See details athttp://www.wescottdesign.com/actfes/actfes.html- Hide quoted text -
>
> - Show quoted text -



Thanks for the useful information.  I'll look more into the specs on
my 78L05.

Say... you wrote "Applied Control Theory for Embedded Systems", eh?
Are Ziegler-Nichols and Cohen-Coon covered in your text?

Thanks,

Michael

m...@gmail.com wrote:
> On Jul 3, 9:17 am, Tim Wescott <t...@seemywebsite.com> wrote:
>> mrdarr...@gmail.com wrote:
>>> I was reading the datasheet on my ATTiny13, and noticed the following
>>> ABSOLUTE MAXIMUM ratings:
>>> Maximum Operating Voltage 6.0V
>>> DC Current Vcc and GND pins:  200 mA
>>> I was planning on powering my device with 4 1.2 NiMH batteries.  Do I
>>> still need a 78L05 voltage regulator, or can I skip that?  (I've got
>>> one just in case, but wondering if it's necessary with 4.8V
>>> nominal...)
>>> Why the restriction on the DC current input?  Won't the device just
>>> suck as much current as it needs?  Or should I put a resistor there in
>>> series with Vcc...?  R=V/I = 5.0V / 0.2A = 25 ohms?
>> NiMH batteries will routinely show 1.25V/cell when they are fully
>> charged, which puts you right at 6V.  1.3V/cell is not unheard of, and
>> that puts you over.  I'd recommend a low drop out* 5V regulator.  Even
>> if you could just go straight off the battery you want to have some
>> healthy capacitance on the power supply line, as batteries have
>> significant internal resistance that can cause supply-line droop, which
>> messes up the processor.
>>
>> The DC current input restriction is there because something in the chip
>> will burn up if you exceed it.  The chip by itself shouldn't consume
>> much power (the amount will be in the data sheet), but you will be
>> driving things from it's output pins -- the maximum current directive is
>> to you, the circuit designer, to make sure you don't hang too many
>> things off of the chip.
>>
>> *  The 78L05 needs more than 1.5V of overhead, depending on whose you
>> buy and how much current you pull -- I figure that 8V into the regulator
>> is the minimum safe value, and I prefer 9V.
>>
>> --
>>
>> Tim Wescott
>> Wescott Design Serviceshttp://www.wescottdesign.com
>>
>> Do you need to implement control loops in software?
>> "Applied Control Theory for Embedded Systems" gives you just what it says.
>> See details athttp://www.wescottdesign.com/actfes/actfes.html- Hide quoted text -
>>
>> - Show quoted text -
> 
> 
> 
> Thanks for the useful information.  I'll look more into the specs on
> my 78L05.
> 
> Say... you wrote "Applied Control Theory for Embedded Systems", eh?
> Are Ziegler-Nichols and Cohen-Coon covered in your text?
> 
No, but if I ever get a chance to do some addenda, Z-N is on my list of 
things to add, and now I'm going to have to familiarize myself with 
Cohen-Coon.

Ziegler-Nichols tuning tends to result in an underdamped system; Astrom 
and Hagglund improved on this in a way that uses the Z-N measurements 
followed by different calculations.

If you can get your hands on the system for long enough, it's much 
better to do a more formal system identification, followed by a 
controller design.  This covers a lot more bases than Z-N tuning does.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

m...@gmail.com wrote:
> On Jul 3, 9:17 am, Tim Wescott <t...@seemywebsite.com> wrote:
> 
>>mrdarr...@gmail.com wrote:
>>
>>>I was reading the datasheet on my ATTiny13, and noticed the following
>>>ABSOLUTE MAXIMUM ratings:
>>
>>>Maximum Operating Voltage 6.0V
>>>DC Current Vcc and GND pins:  200 mA
>>
>>>I was planning on powering my device with 4 1.2 NiMH batteries.  Do I
>>>still need a 78L05 voltage regulator, or can I skip that?  (I've got
>>>one just in case, but wondering if it's necessary with 4.8V
>>>nominal...)
>>
>>>Why the restriction on the DC current input?  Won't the device just
>>>suck as much current as it needs?  Or should I put a resistor there in
>>>series with Vcc...?  R=V/I = 5.0V / 0.2A = 25 ohms?
>>
>>NiMH batteries will routinely show 1.25V/cell when they are fully
>>charged, which puts you right at 6V.  1.3V/cell is not unheard of, and
>>that puts you over.  I'd recommend a low drop out* 5V regulator.  Even
>>if you could just go straight off the battery you want to have some
>>healthy capacitance on the power supply line, as batteries have
>>significant internal resistance that can cause supply-line droop, which
>>messes up the processor.
>>
>>The DC current input restriction is there because something in the chip
>>will burn up if you exceed it.  The chip by itself shouldn't consume
>>much power (the amount will be in the data sheet), but you will be
>>driving things from it's output pins -- the maximum current directive is
>>to you, the circuit designer, to make sure you don't hang too many
>>things off of the chip.
>>
>>*  The 78L05 needs more than 1.5V of overhead, depending on whose you
>>buy and how much current you pull -- I figure that 8V into the regulator
>>is the minimum safe value, and I prefer 9V.
>>
>>--
>>
>>Tim Wescott
>>Wescott Design Serviceshttp://www.wescottdesign.com
>>
>>Do you need to implement control loops in software?
>>"Applied Control Theory for Embedded Systems" gives you just what it says.
>>See details athttp://www.wescottdesign.com/actfes/actfes.html- Hide quoted text -
>>
>>- Show quoted text -
> 
> 
> 
> 
> Thanks for the useful information.  I'll look more into the specs on
> my 78L05.
> 
> Say... you wrote "Applied Control Theory for Embedded Systems", eh?
> Are Ziegler-Nichols and Cohen-Coon covered in your text?
> 
> Thanks,
> 
> Michael
> 

Forget the 78L05 or any other regulator.  You don't need it,
and it won't work, in any event.

You have 4 cells. The maximum voltage per cell is 1.43. So
the maximum total voltage is 5.72, and your device can handle
up to 6.00.  The cells will drop to nominal very quickly, so
you'll have 4.8 volts. No 5 volt regulator will work with 4.8 V
input.

If you *must* have 5.0 volts exactly, you'll either need to
add more cells and a regulator, or use a dc-dc converter, which
*can* produce 5V regulated output with 4.8V input.

Ed

On Jul 3, 8:26 pm, ehsjr <e...@bellatlantic.net> wrote:
> mrdarr...@gmail.com wrote:
> > On Jul 3, 9:17 am, Tim Wescott <t...@seemywebsite.com> wrote:
>
> >>mrdarr...@gmail.com wrote:
>
> >>>I was reading the datasheet on my ATTiny13, and noticed the following
> >>>ABSOLUTE MAXIMUM ratings:
>
> >>>Maximum Operating Voltage 6.0V
> >>>DC Current Vcc and GND pins:  200 mA
>
> >>>I was planning on powering my device with 4 1.2 NiMH batteries.  Do I
> >>>still need a 78L05 voltage regulator, or can I skip that?  (I've got
> >>>one just in case, but wondering if it's necessary with 4.8V
> >>>nominal...)
>
> >>>Why the restriction on the DC current input?  Won't the device just
> >>>suck as much current as it needs?  Or should I put a resistor there in
> >>>series with Vcc...?  R=V/I = 5.0V / 0.2A = 25 ohms?
>
> >>NiMH batteries will routinely show 1.25V/cell when they are fully
> >>charged, which puts you right at 6V.  1.3V/cell is not unheard of, and
> >>that puts you over.  I'd recommend a low drop out* 5V regulator.  Even
> >>if you could just go straight off the battery you want to have some
> >>healthy capacitance on the power supply line, as batteries have
> >>significant internal resistance that can cause supply-line droop, which
> >>messes up the processor.
>
> >>The DC current input restriction is there because something in the chip
> >>will burn up if you exceed it.  The chip by itself shouldn't consume
> >>much power (the amount will be in the data sheet), but you will be
> >>driving things from it's output pins -- the maximum current directive is
> >>to you, the circuit designer, to make sure you don't hang too many
> >>things off of the chip.
>
> >>*  The 78L05 needs more than 1.5V of overhead, depending on whose you
> >>buy and how much current you pull -- I figure that 8V into the regulator
> >>is the minimum safe value, and I prefer 9V.
>
> >>--
>
> >>Tim Wescott
> >>Wescott Design Serviceshttp://www.wescottdesign.com
>
> >>Do you need to implement control loops in software?
> >>"Applied Control Theory for Embedded Systems" gives you just what it says.
> >>See details athttp://www.wescottdesign.com/actfes/actfes.html-Hide quoted text -
>
> >>- Show quoted text -
>
> > Thanks for the useful information.  I'll look more into the specs on
> > my 78L05.
>
> > Say... you wrote "Applied Control Theory for Embedded Systems", eh?
> > Are Ziegler-Nichols and Cohen-Coon covered in your text?
>
> > Thanks,
>
> > Michael
>
> Forget the 78L05 or any other regulator.  You don't need it,
> and it won't work, in any event.
>
> You have 4 cells. The maximum voltage per cell is 1.43. So
> the maximum total voltage is 5.72, and your device can handle
> up to 6.00.  The cells will drop to nominal very quickly, so
> you'll have 4.8 volts. No 5 volt regulator will work with 4.8 V
> input.
>
> If you *must* have 5.0 volts exactly, you'll either need to
> add more cells and a regulator, or use a dc-dc converter, which
> *can* produce 5V regulated output with 4.8V input.
>
> Ed


I could use a 9V batt.  Don't like to, but I could.

I suppose I could even go to Goodwill, get some wall warts for $1, and
use a regulator on that.

I just have a house full of 1.2V NiMHs.

On Jul 3, 6:44 pm, Tim Wescott <t...@seemywebsite.com> wrote:
...

> > Say... you wrote "Applied Control Theory for Embedded Systems", eh?
> > Are Ziegler-Nichols and Cohen-Coon covered in your text?
>
> No, but if I ever get a chance to do some addenda, Z-N is on my list of
> things to add, and now I'm going to have to familiarize myself with
> Cohen-Coon.
>
> Ziegler-Nichols tuning tends to result in an underdamped system; Astrom
> and Hagglund improved on this in a way that uses the Z-N measurements
> followed by different calculations.
>
> If you can get your hands on the system for long enough, it's much
> better to do a more formal system identification, followed by a
> controller design.  This covers a lot more bases than Z-N tuning does.
>
> --
>
> Tim Wescott
> Wescott Design Serviceshttp://www.wescottdesign.com
>
> Do you need to implement control loops in software?
> "Applied Control Theory for Embedded Systems" gives you just what it says.
> See details athttp://www.wescottdesign.com/actfes/actfes.html


I took a process control class in college; didn't learn much from it,
I'm afraid, and I didn't do so great in the class first time around
(wink) - but those terms came up during class (PID controllers,
etc.)

Personally, during class, I wondered why a simple on-off thermostat
couldn't work.  I just couldn't visualize the need for such esoteric
mathematical exercises for control.

If Z-N and Cohen-Coon have been superseded by something even better,
I'm all ears...

Michael

On 2007-07-03, m...@gmail.com <m...@gmail.com> wrote:
> I was reading the datasheet on my ATTiny13, and noticed the following
> ABSOLUTE MAXIMUM ratings:
>
> Maximum Operating Voltage 6.0V
> DC Current Vcc and GND pins:  200 mA
>
> I was planning on powering my device with 4 1.2 NiMH batteries.  Do I
> still need a 78L05 voltage regulator, or can I skip that?  (I've got
> one just in case, but wondering if it's necessary with 4.8V
> nominal...)

If you're going to charge the battery while the controller is
connected, or if you want to protect it against misuse then the regulator
would be needed, but otherwise no.

> Why the restriction on the DC current input?  Won't the device just
> suck as much current as it needs? 

if you put large loads on the output pins those currents flow through VCC or
GND 

Bye.
   Jasen

On 2007-07-03, Tim Wescott <t...@seemywebsite.com> wrote:

> NiMH batteries will routinely show 1.25V/cell when they are fully 
> charged, which puts you right at 6V.  1.3V/cell is not unheard of, and 
> that puts you over.

What is it with arithmetic this week?  everyone seems to be messing it
up!
 
anything less than 1.5v per cell is OK.


-- 

Bye.
   Jasen