| Author |
Message |
Tuurbo46
Guest
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 Posted:
Wed Feb 09, 2005 1:07 am Post subject:
78L05 |
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Hi
Im currently using a 78L05 chip to power up my PIC 16C773 and my 231CPD
driver/ reciver chip. The circuit functions ok when running, but the circuit
is real hard to boot up. When the circuit is connected to Hyper-terminal
when phalse boots occur junk comes through.
The 78L05 is fead with 12V DC on the input and has a 10uF polarised cap
accross this input to ground. When i disconnect this cap the booting becomes
impossible and the junk on hyper-terminal is worse. Therefore if i say put a
100uF cap in place of my 10uF, would this solve all my problems? If so what
is the maths behind it, or is it just a plug and play theory?
After reading through a few of my monthly issues of practical electronics, i
notice that most of the circuits that they build us 100uF! Is this the
reason why they use them?
Cheers Turbo46
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Guest
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| Posted:
Wed Feb 09, 2005 1:15 am Post subject:
Re: 78L05 |
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Tuurbo46 wrote:
| Quote: | The 78L05 is fead with 12V DC on the input and has a 10uF polarised
cap
accross this input to ground. When i disconnect this cap the booting
becomes |
What is the ripple on this "12V DC" input? |
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Michael Black
Guest
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| Posted:
Wed Feb 09, 2005 1:21 am Post subject:
Re: 78L05 |
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"Tuurbo46" (alex@beale55.fsnet.co.uk) writes:
| Quote: | Hi
Im currently using a 78L05 chip to power up my PIC 16C773 and my 231CPD
driver/ reciver chip. The circuit functions ok when running, but the circuit
is real hard to boot up. When the circuit is connected to Hyper-terminal
when phalse boots occur junk comes through.
The 78L05 is fead with 12V DC on the input and has a 10uF polarised cap
accross this input to ground. When i disconnect this cap the booting becomes
impossible and the junk on hyper-terminal is worse. Therefore if i say put a
100uF cap in place of my 10uF, would this solve all my problems? If so what
is the maths behind it, or is it just a plug and play theory?
After reading through a few of my monthly issues of practical electronics, i
notice that most of the circuits that they build us 100uF! Is this the
reason why they use them?
Cheers Turbo46
These three-terminal regulators oscillate, not really a surprise given |
the high gain inside.
If they aren't properly bypassed, they will oscillate.
Read the datasheet. They will only specify an input capacitor if the
regulator is far enough from the filter capacitor in the power supply;
after all there would be a large value there and a small capacitor will
only come into play if there is significant distance.
But they will specify a capacitor on the output. You've mentioned the
input, not the output.
And the type of capacitor affects the value. They will specify that if
a tantalum is used, the value is different from an ordinary electrolytic.
But this is because of the structure of the capacitor.
Larger is not necessarily better, in this case.
Michael
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Tuurbo46
Guest
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| Posted:
Wed Feb 09, 2005 1:24 am Post subject:
Re: 78L05 |
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I think it has zero ripple because it comes from a 12V DC battery. It a
small version of a motorbike battery. |
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John Fields
Guest
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| Posted:
Wed Feb 09, 2005 1:26 am Post subject:
Re: 78L05 |
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On Tue, 8 Feb 2005 19:07:07 -0000, "Tuurbo46"
<alex@beale55.fsnet.co.uk> wrote:
| Quote: | Hi
Im currently using a 78L05 chip to power up my PIC 16C773 and my 231CPD
driver/ reciver chip. The circuit functions ok when running, but the circuit
is real hard to boot up. When the circuit is connected to Hyper-terminal
when phalse boots occur junk comes through.
The 78L05 is fead with 12V DC on the input and has a 10uF polarised cap
accross this input to ground. When i disconnect this cap the booting becomes
impossible and the junk on hyper-terminal is worse. Therefore if i say put a
100uF cap in place of my 10uF, would this solve all my problems?
|
---
Maybe; try it and see...
---
| Quote: | If so what
is the maths behind it, or is it just a plug and play theory?
|
---
Do you really want to know, or do you just want the thing to work?
---
| Quote: | After reading through a few of my monthly issues of practical electronics, i
notice that most of the circuits that they build us 100uF! Is this the
reason why they use them?
|
---
???
--
John Fields |
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Tuurbo46
Guest
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| Posted:
Wed Feb 09, 2005 1:29 am Post subject:
Re: 78L05 |
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Ur um, the thing to work please. lol
"John Fields" <jfields@austininstruments.com> wrote in message
news:gb4i01d4vp23hb3q5fghm2d0sja11qn3d3@4ax.com...
| Quote: | On Tue, 8 Feb 2005 19:07:07 -0000, "Tuurbo46"
alex@beale55.fsnet.co.uk> wrote:
Hi
Im currently using a 78L05 chip to power up my PIC 16C773 and my 231CPD
driver/ reciver chip. The circuit functions ok when running, but the
circuit
is real hard to boot up. When the circuit is connected to Hyper-terminal
when phalse boots occur junk comes through.
The 78L05 is fead with 12V DC on the input and has a 10uF polarised cap
accross this input to ground. When i disconnect this cap the booting
becomes
impossible and the junk on hyper-terminal is worse. Therefore if i say put
a
100uF cap in place of my 10uF, would this solve all my problems?
---
Maybe; try it and see...
---
If so what
is the maths behind it, or is it just a plug and play theory?
---
Do you really want to know, or do you just want the thing to work?
---
After reading through a few of my monthly issues of practical electronics,
i
notice that most of the circuits that they build us 100uF! Is this the
reason why they use them?
---
???
--
John Fields |
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Anthony Fremont
Guest
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| Posted:
Wed Feb 09, 2005 1:55 am Post subject:
Re: 78L05 |
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"Tuurbo46" <alex@beale55.fsnet.co.uk> wrote
| Quote: | Ur um, the thing to work please. lol
|
Then put a .01uF cap on the output and maybe a 1uF as well. I wouldn't
use more capacitance on the output than on the input.
Add seperate bypass caps to the PIC unless you like allot of mysterious
resets. PIC chips are fussy about how fast Vdd ramps up too. If it
comes up too slow (>100mS), then the PIC won't come out of reset.
BTW, please don't top post. |
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John Fields
Guest
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| Posted:
Wed Feb 09, 2005 2:08 am Post subject:
Re: 78L05 |
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|
On Tue, 8 Feb 2005 19:29:55 -0000, "Tuurbo46"
<alex@beale55.fsnet.co.uk> wrote:
| Quote: | Ur um, the thing to work please. lol
|
---
Tell us what else you've got hooked to the battery, where it's hooked
up and how long the wires are, and how long the wires are going from
the battery to the regulator. Also, do you have anything else hooked
to the +5 side of the regulator other than the 2 chips you already
mentioned?
--
John Fields |
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Leon Heller
Guest
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| Posted:
Wed Feb 09, 2005 2:43 am Post subject:
Re: 78L05 |
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"Tuurbo46" <alex@beale55.fsnet.co.uk> wrote in message
news:cub2kr$j7q$1@news8.svr.pol.co.uk...
| Quote: | Hi
Im currently using a 78L05 chip to power up my PIC 16C773 and my 231CPD
driver/ reciver chip. The circuit functions ok when running, but the
circuit is real hard to boot up. When the circuit is connected to
Hyper-terminal when phalse boots occur junk comes through.
The 78L05 is fead with 12V DC on the input and has a 10uF polarised cap
accross this input to ground. When i disconnect this cap the booting
becomes impossible and the junk on hyper-terminal is worse. Therefore if i
say put a 100uF cap in place of my 10uF, would this solve all my problems?
If so what is the maths behind it, or is it just a plug and play theory?
After reading through a few of my monthly issues of practical electronics,
i notice that most of the circuits that they build us 100uF! Is this the
reason why they use them?
|
I think the 78L05 data sheet suggests a 330 nF capacitor on the input.
Leon
--
Leon Heller, G1HSM
http://www.geocities.com/leon_heller |
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Mark Jones
Guest
|
| Posted:
Wed Feb 09, 2005 4:42 am Post subject:
Re: 78L05 |
|
|
Tuurbo46 wrote:
| Quote: | I think it has zero ripple because it comes from a 12V DC battery. It a
small version of a motorbike battery.
|
And does this motorbike battery have a charger? If it does, does the charger
put out any ripple? Any vehicle is going to have horrendous spikes from the
charging system. Ripple from these chargers will go straight past the battery
and cause problems unless designed around. |
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petrus bitbyter
Guest
|
| Posted:
Wed Feb 09, 2005 5:31 am Post subject:
Re: 78L05 |
|
|
"Tuurbo46" <alex@beale55.fsnet.co.uk> schreef in bericht
news:cub2kr$j7q$1@news8.svr.pol.co.uk...
| Quote: | Hi
Im currently using a 78L05 chip to power up my PIC 16C773 and my 231CPD
driver/ reciver chip. The circuit functions ok when running, but the
circuit is real hard to boot up. When the circuit is connected to
Hyper-terminal when phalse boots occur junk comes through.
The 78L05 is fead with 12V DC on the input and has a 10uF polarised cap
accross this input to ground. When i disconnect this cap the booting
becomes impossible and the junk on hyper-terminal is worse. Therefore if i
say put a 100uF cap in place of my 10uF, would this solve all my problems?
If so what is the maths behind it, or is it just a plug and play theory?
After reading through a few of my monthly issues of practical electronics,
i notice that most of the circuits that they build us 100uF! Is this the
reason why they use them?
Cheers Turbo46
|
Well,
First of all, get the datasheet. It is advised to use a 330nF capacitor on
the input and a 100nF one on the output. Ceramic types are prefered and you
have to mount them just beside the regulator. Then be sure to decouple every
chip with a 10-100nF ceramic capacitor. Unless you have a very noisy
environment this should do.
But, if not: Are you sure the current does not exceeds the 100mA rating
during power up? Is it possible that powerdissipation is too high during
boot? Do you have long lines between the 12V source and the regulator
and/or between the regulator and the load? These can be a reason to add
elco's for decoupling. Are other devices then the ones you mentioned
connected to the output? Devices that can do weird things at power up?
petrus bitbyter |
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Fred Bloggs
Guest
|
| Posted:
Wed Feb 09, 2005 7:40 am Post subject:
Re: 78L05 |
|
|
Tuurbo46 wrote:
| Quote: | Hi
Im currently using a 78L05 chip to power up my PIC 16C773 and my 231CPD
driver/ reciver chip. The circuit functions ok when running, but the circuit
is real hard to boot up. When the circuit is connected to Hyper-terminal
when phalse boots occur junk comes through.
The 78L05 is fead with 12V DC on the input and has a 10uF polarised cap
accross this input to ground. When i disconnect this cap the booting becomes
impossible and the junk on hyper-terminal is worse. Therefore if i say put a
100uF cap in place of my 10uF, would this solve all my problems? If so what
is the maths behind it, or is it just a plug and play theory?
After reading through a few of my monthly issues of practical electronics, i
notice that most of the circuits that they build us 100uF! Is this the
reason why they use them?
Cheers Turbo46
|
You're slamming the 78L05 with a helluva transient unnecessarily and
this is interfering with the PIC power-on reset. Use a current surge
limiting resistor:
View in a fixed-width font such as Courier.
78L05
/ 47 1W +-------+
BATT>-o o----/\/\--+----------+----|IN OUT|--+----
|+ | | | |
=== === | GND | ===
|10U |330n+-------+ |100n
| | | |
| | | |
GND >--------------+----------+--------+------+----- |
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Rich Grise
Guest
|
| Posted:
Wed Feb 09, 2005 8:06 am Post subject:
Re: 78L05 |
|
|
On Tue, 08 Feb 2005 19:07:07 +0000, Tuurbo46 wrote:
| Quote: | Hi
Im currently using a 78L05 chip to power up my PIC 16C773 and my 231CPD
driver/ reciver chip. The circuit functions ok when running, but the circuit
is real hard to boot up. When the circuit is connected to Hyper-terminal
when phalse boots occur junk comes through.
The 78L05 is fead with 12V DC on the input and has a 10uF polarised cap
accross this input to ground. When i disconnect this cap the booting becomes
impossible and the junk on hyper-terminal is worse. Therefore if i say put a
100uF cap in place of my 10uF, would this solve all my problems? If so what
is the maths behind it, or is it just a plug and play theory?
After reading through a few of my monthly issues of practical electronics, i
notice that most of the circuits that they build us 100uF! Is this the
reason why they use them?
|
In the time it took you to write this, you could have already put in the
100 uF. Why do you hesitate?
Good Luck!
Rich |
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Rich Grise
Guest
|
| Posted:
Wed Feb 09, 2005 8:07 am Post subject:
Re: 78L05 |
|
|
On Tue, 08 Feb 2005 17:42:59 -0500, Mark Jones wrote:
| Quote: | Tuurbo46 wrote:
I think it has zero ripple because it comes from a 12V DC battery. It a
small version of a motorbike battery.
And does this motorbike battery have a charger? If it does, does the charger
put out any ripple? Any vehicle is going to have horrendous spikes from the
charging system. Ripple from these chargers will go straight past the battery
and cause problems unless designed around.
|
In which case he also needs a hash choke.
Cheers!
Rich |
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Rene Tschaggelar
Guest
|
| Posted:
Wed Feb 09, 2005 8:40 am Post subject:
Re: 78L05 |
|
|
Tuurbo46 wrote:
| Quote: | Hi
Im currently using a 78L05 chip to power up my PIC 16C773 and my 231CPD
driver/ reciver chip. The circuit functions ok when running, but the circuit
is real hard to boot up. When the circuit is connected to Hyper-terminal
when phalse boots occur junk comes through.
The 78L05 is fead with 12V DC on the input and has a 10uF polarised cap
accross this input to ground. When i disconnect this cap the booting becomes
impossible and the junk on hyper-terminal is worse. Therefore if i say put a
100uF cap in place of my 10uF, would this solve all my problems? If so what
is the maths behind it, or is it just a plug and play theory?
After reading through a few of my monthly issues of practical electronics, i
notice that most of the circuits that they build us 100uF! Is this the
reason why they use them?
|
How about having a look at the waveforms with a scope ?
Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net |
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