5 volt out of 6 volt Battery pack

Archiver

hello,
i'm new in this group.

I spent a couple of days reading your different messages and found
already a lot of interresting things. My problem is that i understand
the programming side of the BS2, but basic electronic may sometimes
be difficult. I try to create a small datalogger for my RC Car (1/10
nitro on-road)

http://www.rc10.com/shusting/CatalogHub/kitspecs_ntc3/kitntc3.htm

The mainboard will include a BS2P, a PAk7, and a 24Cxxx eeprom with
associated pull up resistors on the i/o lines. Sensors will be off
board, 4 hall latched sensors ( one per whell) and the Memsic, all
connected to the Pak 7.

My main problem is how to power my board as i must use the RX battery
(6v 1100 mah NiMh) as power source? I imagine two different scenario
but to many unsolved questions

First the 7805 chip but some comments say that you need around 8v
input to have a stable 5v output. Is this correct or will it work
with 6 volt?

Second would it be possible to bring 6v to the Vin of the BS2p and
use the output 5VDD to power to memsic and eeprom. Stay the Pak7 to
power will he accept 6v?

I'm using the free demo version of Eagle to create this board

Thank you

Archiver

In my search i found this

http://myhome.spu.edu/bolding/EE1210/ee1210_assignments/lab1.htm

Will it work for my board?
Will a single diode be sufficient or would it be better to give every
component (BS2P,Pak7,EPROOM) is own diode?

Archiver

The BS2 has on-module a low-dropout linear regulator.
'Low-dropout' means the voltage difference between
the Vin and the Vregulated_out is 'low' -- for a
7805, it's about 1.4 volts which is 'typical'.
Thus, 6 volts - 1.4 volts == 4.6 volts, which
won't work (it's too far below 5 volts).

I think it's around 0.6 volts for the BS2, which
is considered 'low-dropout', so 6 volts will
work.

This means you can drive it with 6 volts to 9 volts,
and the on-chip regulator will adjust it to 5.0
volts for the BS2. You can also use 50mA or so
from the BS2 to drive other circuits -- but
you MUST be careful with this. If you use too
much current from the BS2, the regulator will
go into thermal shutdown. I don't know what
the current requirments are for your other
devices.

This all means that if you have a large (10uF)
capacitor and a small (.1 uF) cap near the
BS2, you could use the single 6V battery for
both the motors and the BS2. The caps are to
provide filtering for the BS2 from the noise
of the motors.

You could also use a low-dropout external
regulator, to get both your desired current
and voltage from a 6 volt battery.

--- In basicstamps@yahoogroups.com, "le_pev" <didier.pevenage@b...>
wrote:
> hello,
> i'm new in this group.
>
> I spent a couple of days reading your different messages and found
> already a lot of interresting things. My problem is that i
understand
> the programming side of the BS2, but basic electronic may sometimes
> be difficult. I try to create a small datalogger for my RC Car
(1/10
> nitro on-road)
>
> http://www.rc10.com/shusting/CatalogHub/kitspecs_ntc3/kitntc3.htm
>
> The mainboard will include a BS2P, a PAk7, and a 24Cxxx eeprom with
> associated pull up resistors on the i/o lines. Sensors will be off
> board, 4 hall latched sensors ( one per whell) and the Memsic, all
> connected to the Pak 7.
>
> My main problem is how to power my board as i must use the RX
battery
> (6v 1100 mah NiMh) as power source? I imagine two different
scenario
> but to many unsolved questions
>
> First the 7805 chip but some comments say that you need around 8v
> input to have a stable 5v output. Is this correct or will it work
> with 6 volt?
>
> Second would it be possible to bring 6v to the Vin of the BS2p and
> use the output 5VDD to power to memsic and eeprom. Stay the Pak7 to
> power will he accept 6v?
>
> I'm using the free demo version of Eagle to create this board
>
> Thank you

Archiver

Thank you for your answer Allan.
The datasheet for the eeprom give a consumption of 5 mA in write
conditions. And the memsic is advertised as consuming 4 mA on the
parallax site. So the on chip regulator will be good for these two
devices. I just need to know if the PAk 7 will work under 6 volts.

Anyway do you have reference for a low dropout external voltage
regulator?

--- In basicstamps@yahoogroups.com, "Allan Lane" <allan.lane@h...>
wrote:
> The BS2 has on-module a low-dropout linear regulator.
> 'Low-dropout' means the voltage difference between
> the Vin and the Vregulated_out is 'low' -- for a
> 7805, it's about 1.4 volts which is 'typical'.
> Thus, 6 volts - 1.4 volts == 4.6 volts, which
> won't work (it's too far below 5 volts).
>
> I think it's around 0.6 volts for the BS2, which
> is considered 'low-dropout', so 6 volts will
> work.
>
> This means you can drive it with 6 volts to 9 volts,
> and the on-chip regulator will adjust it to 5.0
> volts for the BS2. You can also use 50mA or so
> from the BS2 to drive other circuits -- but
> you MUST be careful with this. If you use too
> much current from the BS2, the regulator will
> go into thermal shutdown. I don't know what
> the current requirments are for your other
> devices.
>
> This all means that if you have a large (10uF)
> capacitor and a small (.1 uF) cap near the
> BS2, you could use the single 6V battery for
> both the motors and the BS2. The caps are to
> provide filtering for the BS2 from the noise
> of the motors.
>
> You could also use a low-dropout external
> regulator, to get both your desired current
> and voltage from a 6 volt battery.
>

Archiver

I knew you'd ask if I didn't put it in, but I
was lazy last time.

National Semiconductor LM2940 (1Amp,
.5 volt dropout)

LM2936-5, which has .2 volt dropout, and
15 uA quiescent current.

--- In basicstamps@yahoogroups.com, "le_pev" <didier.pevenage@b...>
wrote:
> Thank you for your answer Allan.
> The datasheet for the eeprom give a consumption of 5 mA in write
> conditions. And the memsic is advertised as consuming 4 mA on the
> parallax site. So the on chip regulator will be good for these two
> devices. I just need to know if the PAk 7 will work under 6 volts.
>
> Anyway do you have reference for a low dropout external voltage
> regulator?
>
> --- In basicstamps@yahoogroups.com, "Allan Lane" <allan.lane@h...>
> wrote:
> > The BS2 has on-module a low-dropout linear regulator.
> > 'Low-dropout' means the voltage difference between
> > the Vin and the Vregulated_out is 'low' -- for a
> > 7805, it's about 1.4 volts which is 'typical'.
> > Thus, 6 volts - 1.4 volts == 4.6 volts, which
> > won't work (it's too far below 5 volts).
> >
> > I think it's around 0.6 volts for the BS2, which
> > is considered 'low-dropout', so 6 volts will
> > work.
> >
> > This means you can drive it with 6 volts to 9 volts,
> > and the on-chip regulator will adjust it to 5.0
> > volts for the BS2. You can also use 50mA or so
> > from the BS2 to drive other circuits -- but
> > you MUST be careful with this. If you use too
> > much current from the BS2, the regulator will
> > go into thermal shutdown. I don't know what
> > the current requirments are for your other
> > devices.
> >
> > This all means that if you have a large (10uF)
> > capacitor and a small (.1 uF) cap near the
> > BS2, you could use the single 6V battery for
> > both the motors and the BS2. The caps are to
> > provide filtering for the BS2 from the noise
> > of the motors.
> >
> > You could also use a low-dropout external
> > regulator, to get both your desired current
> > and voltage from a 6 volt battery.
> >

Archiver

Thank you again LM2940 is already inserted in my board drawing with 2
associated caps. Will each chip still require an extra cap for
filtering of VCC?

Its sunday, your free to be lazy ;-))

--- In basicstamps@yahoogroups.com, "Allan Lane" <allan.lane@h...>
wrote:
> I knew you'd ask if I didn't put it in, but I
> was lazy last time.
>
> National Semiconductor LM2940 (1Amp,
> .5 volt dropout)
>
> LM2936-5, which has .2 volt dropout, and
> 15 uA quiescent current.
>

Archiver

It's a very good idea to place a 0.1 uF bypass cap at each IC, mounted as
close to the chip's power pins as possible. Here is a nice article about
the reasons for the bypass caps, as well as other related topics:

http://www.glencoe.com/ps/ee/williamson/bypass.html

Also, be sure to check the LM2940's data sheet carefully with regard to the
"ESR" value required for the output capacitor.

Randy

www.glitchbuster.com

---

Original Message

---

From: "le_pev" <didier.pevenage@b...>
To: <basicstamps@yahoogroups.com>
Sent: Sunday, June 29, 2003 12:32 PM
Subject: [noparse][[/noparse]basicstamps] Re: 5 volt out of 6 volt Battery pack


> Thank you again LM2940 is already inserted in my board drawing with 2
> associated caps. Will each chip still require an extra cap for
> filtering of VCC?
>
> Its sunday, your free to be lazy ;-))
>
> --- In basicstamps@yahoogroups.com, "Allan Lane" <allan.lane@h...>
> wrote:
> > I knew you'd ask if I didn't put it in, but I
> > was lazy last time.
> >
> > National Semiconductor LM2940 (1Amp,
> > .5 volt dropout)
> >
> > LM2936-5, which has .2 volt dropout, and
> > 15 uA quiescent current.
> >
>
>
>
> To UNSUBSCRIBE, just send mail to:
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Body of the message will be ignored.
>
>
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>
>

Archiver

In a message dated 6/29/2003 12:34:05 PM Pacific Daylight Time,
didier.pevenage@b... writes:

> Thank you again LM2940 is already inserted in my board drawing with 2
> associated caps. Will each chip still require an extra cap for
> filtering of VCC?
>

It is almost ALWAYS a good idea to install a 0.1 uF cap as close to the IC as
possible from VCC to VSS.


[noparse][[/noparse]Non-text portions of this message have been removed]

Archiver

For digital logic, and especially digital logic
running with motors, a 'local' de-coupling
capacitor of .1 uF ('local' meaning sitting
across +5 and GND very close to the chip's
+5 and GND pins) is a good idea.

Digital logic can have low continuous current
needs, then have a 'spike' of current needed
for switching transients. A local capacitor
supplies the current pulse needed. Without
it, the current spike can result in a
voltage drop. If the voltage drop is
severe enough, it can reset the chip, or
result in un-predictable behavior.

So yes, I'd put an addition 0.1 uF cap
near each chip.

--- In basicstamps@yahoogroups.com, "le_pev" <didier.pevenage@b...>
wrote:
> Thank you again LM2940 is already inserted in my board drawing with
2
> associated caps. Will each chip still require an extra cap for
> filtering of VCC?
>
> Its sunday, your free to be lazy ;-))
>
> --- In basicstamps@yahoogroups.com, "Allan Lane" <allan.lane@h...>
> wrote:
> > I knew you'd ask if I didn't put it in, but I
> > was lazy last time.
> >
> > National Semiconductor LM2940 (1Amp,
> > .5 volt dropout)
> >
> > LM2936-5, which has .2 volt dropout, and
> > 15 uA quiescent current.
> >