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'[PIC]: 12V supply for programmers'
2002\07\26@031827 by Kieren Johnstone

picon face
Hi,
Just wondering, will a small 12V alkaline battery (it's about AA size) be OK for a 12V source for use in a PIC programmer - PARPIC, for example.  Or should I go for the 8xAA (or 10xAA rechargable - they're only 1.2V!)?  Or a car battery? :(

Thanks,
Kieren Johnstone

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2002\07\26@081458 by Rick C.

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You can probably use almost any source of power as long as it doesn't dip too far when it goes into programming mode. Not familiar with your programmer but most programmers have a built in regulator for the voltage sensitive parts. Try putting
an milliammeter on your working supply and watch the current when going into programming mode. Shouldn't be all that high anyway. Just make sure your battery supply can provide the equivalent current and then some. I suspect you can use almost
any battery so as long as your voltage is around 12 volts.
Rick

Kieren Johnstone wrote:

> Hi,
> Just wondering, will a small 12V alkaline battery (it's about AA size) be OK for a 12V source for use in a PIC programmer - PARPIC, for example.  Or should I go for the 8xAA (or 10xAA rechargable - they're only 1.2V!)?  Or a car battery? :(
>
> Thanks,
> Kieren Johnstone
>
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2002\07\26@112909 by Richard Mellina

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       You could, but there are a few things to think about.

1. the pic requires between 12V and 14V so I would say that 12V is cutting
it close.

2. If the programming circuit gets its power from the battery and a voltage
regulator then very quickly the battery voltage will be below 12V and the
pic will not program.

3. If you are only using the battery for MCLR then it is probably okay
because all MCLR needs to enter programming mode is a voltage so it will
draw no current. (If I'm not right about this I will probably be corrected.

Hope this helped!



{Original Message removed}

2002\07\26@121043 by Brendan Moran

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>        You could, but there are a few things to think about.
> >
> 1. the pic requires between 12V and 14V so I would say that 12V is
> cutting it close.
>
> 2. If the programming circuit gets its power from the battery and a
> voltage regulator then very quickly the battery voltage will be
> below 12V and the pic will not program.
>
> 3. If you are only using the battery for MCLR then it is probably
> okay because all MCLR needs to enter programming mode is a voltage
> so it will draw no current. (If I'm not right about this I will
> probably be corrected.

You can just add another battery in series, and get 13.5V and then
not worry about dips.

- --Brendan

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2002\07\26@165506 by M. Adam Davis
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You should be able to get current/voltage curves for this device from a
few different battery manufacturers.

The 12V value is known as the 'nominal' voltage, and the actual voltage
before discharge may be as much as a volt or two higher.

If you can't get a dischare curve, then put the battery under load and
measure it every so often to see how much current you can draw for how
long before it drops below the necessary programming voltage.

Chances are good that you won't be able to run the whole programmer from
it, but if you use it with a 4AA supply (4AA for the rest of the
programmer, 12v for the MCLR) then you shouldn't have any problems.

IIRC, most pics have a recommended programming voltage of 13.5 for MCLR.
The ICD (original) documents has a simple PWM controlled voltage
tripler that uses a few transisters, coils, diodes, etc for its
programming voltage.  I would suggest you spend the extra doller for a
handful of parts and derive the programming voltage from your other
power supply (4AA, maybe.)

-Adam

Kieren Johnstone wrote:

{Quote hidden}

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2002\07\26@172629 by Kieren Johnstone

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Thanks for your replies everyone :)  I think I'll build a thingywotsit
socket for use with a "walwart" (must be an American term!..).  My brain
tells me that a 7805 regulates to 5V, so a 7812 will regulate 12V.. is it
lying?  Also, what would I actually have to get from the wallmart (above the
12V)?

Ta
Kieren and his Fish

{Original Message removed}

2002\07\26@201519 by Rick C.

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Correct on the 78xx's. DC wall warts usually only have a diode and one capacitor
in them. Unloaded, they will put out 1.4 times the voltage stated on the warts.
I use 9vdc wall warts for programming modules such as the Warp13 and the
Microchip ICD. 12 volt ones will work just fine too (which they are rated for)
but the 7805 may get a little hotter since they have no heatsink, but they'll
take it. Don't use a 15-18 volt unit because the regulators will get very hot
and may shut down. Besides, they'll leave a blister on your finger.
Rick

Kieren Johnstone wrote:

> Thanks for your replies everyone :)  I think I'll build a thingywotsit
> socket for use with a "walwart" (must be an American term!..).  My brain
> tells me that a 7805 regulates to 5V, so a 7812 will regulate 12V.. is it
> lying?  Also, what would I actually have to get from the wallmart (above the
> 12V)?
>
> Ta
> Kieren and his Fish
>
> {Original Message removed}

2002\07\27@024828 by Kieren Johnstone

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Well, I found this...

www.maplin.co.uk/products/Module.asp?CartID=0207270744491441254&modul
eno=19160&modulecode=

It says it's a regulated 12V supply - could I use this (instead of a 13V
supply w/ 7812 regulator)?

{Original Message removed}

2002\07\27@031438 by Jinx

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> (instead of a 13V supply w/ 7812 regulator)?

If you look up the data for the 7812 you'll see, amongst other
things that the recommended lowest input voltage to maintain
regulation is 14.7V. Also, the best figure for through-current
is when there is a 7V differential, ie when the input voltage is
19V. You won't do any harm by inputting at less than 14.7V
but you'll find that in some circumstances you'll miss out on
the benefits of using a regulator. It's worth getting a data
sheet from one of the big producers, eg Motorola, Fairchild,
National etc, as there are some application notes that will
help you, for example jacking up and bypassing. Just Google
for it

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2002\07\27@032732 by Kieren Johnstone

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It's sort of a bonus, because as far as I can tell 13V adapters are "rare" -
only 12V then 15V are commonly used.  But still, does the "regulated 12V
adapter" mean I don't need a regulating circuit?  I just "connect the
terminals"?

{Original Message removed}

2002\07\27@105755 by Rick C.

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face
Just measure the wall wart with no load and if it hovers at around 12 volts,
then it should work. But I don't know of a programmer that doesn't use an on
board regulator. As a general rule, most circuits will use an on board
regulator. It provides a measure of isolation/protection of the circuit. Sure,
you can use a regulated supply driving another regulated supply but you just
have to remember that a regulated supply requires a voltage significantly higher
than the regulator.
Rick

Kieren Johnstone wrote:

> It's sort of a bonus, because as far as I can tell 13V adapters are "rare" -
> only 12V then 15V are commonly used.  But still, does the "regulated 12V
> adapter" mean I don't need a regulating circuit?  I just "connect the
> terminals"?
>
> {Original Message removed}

2002\07\27@134240 by Byron A Jeff

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On Sat, Jul 27, 2002 at 08:26:34AM +0100, Kieren Johnstone wrote:
> It's sort of a bonus, because as far as I can tell 13V adapters are "rare" -
> only 12V then 15V are commonly used.  But still, does the "regulated 12V
> adapter" mean I don't need a regulating circuit?  I just "connect the
> terminals"?

Probably not a good idea. Let me see if I can review this thread...

(Virtual time passes.... DING!)

OK I'm back. Jinx has most of this covered. I just want to throw in a few
observations:

1) The Vpp voltage required depends on the chip. The Flash parts only use it
as an indicator and it draws no significant current and is specified only to
have to be 3.5-4.5V above Vdd. However for EPROM based parts both the voltage
and current are required to do the actual programming.

2) Behaviorally linear regulators are simple creatures. Here are the basic
rules:

A) Keep an input headroom voltage available. This is generally between 3V-4V
above the regulated voltage.

B) Use filtering caps as specified in the data sheet.

C) Fixed regulator voltages can be varied as their job is to keep the voltage
between the output and GND terminals constant. So to get in the ballpark of
13V you can use a 12V regulator with a diode or two between the GND terminal
and actual GND. Each diode will add about 0.6V to the output voltage. So
one diode will get you 12.6V and two will get you 13.2V using a 12V regulator.

3) And lastly, and I want to reiterate it so that it's very clear, with the
emphasis mine: 13V IS THE PROPER Vpp VOLTAGE, NOT 12V!!!

BAJ

>
> {Original Message removed}

2002\07\27@161157 by Shawn Mulligan

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There's a good chance that a wallwart adapter marked "12V" is really more
like 13.5V or greater. I just bought some surplus adapters for use around
the lab and the 12V models are 20V, under load, (which is unusually high and
may be why they were 'surplus') and the 5V Nokia adapters are 6V, loaded.

-Shawn


Kieren Johnstone wrote:
> > It's sort of a bonus, because as far as I can tell 13V adapters are
>"rare" -
> > only 12V then 15V are commonly used.  But still, does the "regulated 12V
> > adapter" mean I don't need a regulating circuit?  I just "connect the
> > terminals"?


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2002\07\27@172029 by Kieren Johnstone

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Now, call me stupid but:

"Vdd for Alog. 1: min 2.2, max 5.5 (V)"
"Vdd for Alog. 2: min 4.5, max 5.5 (V)"
"High Voltage on MCLR for high voltage programming entry: min Vdd+3.5, max
13.5V"

As I see it, the maximum Vdd is 5.5, so the minimum for high voltage is
3.5+5.5=9V... no? :)

(39025f.pdf, EEPROM Memory Programming Specification - PIC16F87X)

-Kieren

{Original Message removed}

2002\07\27@183527 by Jinx

face picon face
> As I see it, the maximum Vdd is 5.5, so the minimum for high voltage is
> 3.5+5.5=9V... no? :)

That's at odds with Paragraph 1.1 of the same document which
says 13V +/- 0.5V for Microchip's "normal" method and Vdd for
LVP. I can't comment on other programmers but the Picstart Plus
is bang-on 13V. From previous experience making standard
EPROM programmers Vpp +/- 0.5V is the range that you can
be sure that data will stick. Below that and you may have incomplete
writes and above it you'll likely frizz the programming pin (14V max)

Byron mentioned using diodes to raise the o/p voltage of the
regulator. That's what I meant by "jacking up", if you didn't
know. You can also do the same with a couple resistors. The
(usually) middle pin of a regulator is not Ground as such, but
a reference that can be raised above ground and so raise
the o/p voltage

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2002\07\27@234523 by Byron A Jeff

face picon face
On Sat, Jul 27, 2002 at 09:15:47PM +0100, Kieren Johnstone wrote:
> Now, call me stupid but:
>
> "Vdd for Alog. 1: min 2.2, max 5.5 (V)"
> "Vdd for Alog. 2: min 4.5, max 5.5 (V)"
> "High Voltage on MCLR for high voltage programming entry: min Vdd+3.5, max
> 13.5V"
>
> As I see it, the maximum Vdd is 5.5, so the minimum for high voltage is
> 3.5+5.5=9V... no? :)
>
> (39025f.pdf, EEPROM Memory Programming Specification - PIC16F87X)

Not in the least. You're more up to date than I. The 16F87X progspec I had
on my machine is an older version (30262E) that states 13V with a Vdd+3.5
maintenance voltage. The one you quote has the numbers above.

Again be aware that this applies to flash parts only. And I believe this is
the first time that you actually specified a chip.

BAJ

>
> -Kieren
>
> {Original Message removed}

2002\07\29@040445 by Alan B. Pearce

face picon face
>IIRC, most pics have a recommended programming voltage of 13.5 for MCLR.
> The ICD (original) documents has a simple PWM controlled voltage
>tripler that uses a few transisters, coils, diodes, etc for its
>programming voltage.  I would suggest you spend the extra doller for a
>handful of parts and derive the programming voltage from your other
>power supply (4AA, maybe.)

Do be aware that this circuit is sensitive to the inductor used versus the
drive waveform. If using an inductor with high resistance you don't get the
voltage you expect. :)

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