How would you increase current?
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I am building a project with my basic stamp. I will use a ua7805
voltage regulator. The regulator only puts out 1.5 Amps and I need
2 Amps to drive my high-current circuit. Can I simply put two
ua7805's in parallel. Or is there another way of doing this. I am
using a 12 Vdc 7A battery.
voltage regulator. The regulator only puts out 1.5 Amps and I need
2 Amps to drive my high-current circuit. Can I simply put two
ua7805's in parallel. Or is there another way of doing this. I am
using a 12 Vdc 7A battery.
Comments
It is not advised to parallel vRegs. One of them will wind up doing most of
the work. Can you split the load, and use one vReg for each side? This is an
approach that I have used. Or, you can get a Vreg that will handle the
current you need.
Jonathan
www.madlabs.info
Original Message
From: "lanceallenr" <lanceallenr@y...>
To: <basicstamps@yahoogroups.com>
Sent: Wednesday, February 04, 2004 7:29 PM
Subject: [noparse][[/noparse]basicstamps] How would you increase current?
> I am building a project with my basic stamp. I will use a ua7805
> voltage regulator. The regulator only puts out 1.5 Amps and I need
> 2 Amps to drive my high-current circuit. Can I simply put two
> ua7805's in parallel. Or is there another way of doing this. I am
> using a 12 Vdc 7A battery.
>
>
>
>
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one will tend to take more load than the other.
Look at http://www.national.com/ds/LM/LM340.pdf and look at the circuits at
the end. These circuits use a pass transistor. The one with two transistors
is nice because it lets the regulators short circuit and thermal protection
work.
Regards,
AL Williams
AWC
*New: Universal PCB holds Stamps or any micro
http://www.awce.com/gpmpu40.htm
Original Message
From: lanceallenr [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=-AIzb5nWA3NUKmEPfQ3j88VYwsdNTAFfhmjg6Fo1-Yub10W4-7W9rov9sq4BnIdqnsPAuGgmAe5rJzuwjNvY6g]lanceallenr@y...[/url
Sent: Wednesday, February 04, 2004 9:30 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] How would you increase current?
I am building a project with my basic stamp. I will use a ua7805
voltage regulator. The regulator only puts out 1.5 Amps and I need
2 Amps to drive my high-current circuit. Can I simply put two
ua7805's in parallel. Or is there another way of doing this. I am
using a 12 Vdc 7A battery.
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
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efficient and will increase your battery life. But they are more expensive.
They switch the voltage rapidly from 0 to 12 volts and regulate the ooutput by
PWM. The net effect is much more of the input power goes to the load and very
little heat is generated.
A linear regulator sheds the excess volts as heat. 12 volts - 5 volts = 7
volts.
7 volts at 2 amps = 14 watts as wasted heat. You will be wasting almost 60%
of your battery power as heat.
The Digikey catalog has about 3-4 pages of regulators. I do not have one
handy right now, or I would give you some suggestions.
Let me know if you need more info. I can get some numbers when I get back to
the office in a few days.
Alan Bradford
Plasma Technologies
In a message dated 2/5/2004 4:03:10 AM Eastern Standard Time,
lanceallenr@y... writes:
I am building a project with my basic stamp. I will use a ua7805
voltage regulator. The regulator only puts out 1.5 Amps and I need
2 Amps to drive my high-current circuit. Can I simply put two
ua7805's in parallel. Or is there another way of doing this. I am
using a 12 Vdc 7A battery.
[noparse][[/noparse]Non-text portions of this message have been removed]
1. Use one 7805 for your BS2 current, and a
separate one for the 'high-current' line. DON'T
connect the two +5 volt lines together. DO connect
both grounds together. DO use capacitors to
provide clean power to the BS2.
2. Use one TO-3 can LM338 adjustable regulator,
good to 5 amps, supporting current pulses to
7 amps.
--- In basicstamps@yahoogroups.com, "lanceallenr" <lanceallenr@y...>
wrote:
> I am building a project with my basic stamp. I will use a ua7805
> voltage regulator. The regulator only puts out 1.5 Amps and I need
> 2 Amps to drive my high-current circuit. Can I simply put two
> ua7805's in parallel. Or is there another way of doing this. I am
> using a 12 Vdc 7A battery.
different 5 Volt supplies. One of the worst troubleshooting nightmares I
have had was where one 5 Volt regulator output was connected to the output
of another one, in another chassis, across the room. There would be times
where one would want to pull up, the other pull down, they would fight, and
both get very hot. The circuits didn't work either<G>.
Also, if you look, many of the three terminal regulators are more power
limited than current limited. Look at the current you wish to draw, say 1.5
Amps. If you are drawing it from a 12 Volt supply, that is 7 Volts time 2
Amps, which gives 14 Watts of dissipation in the regulator. This means a
good heat sink, a little air flow, or both. I have used a dropping resistor
in series with the regulator at times, but remember that regulators require
a minimum of 3-3.5 Volts across them to be able to work. You have to also
figure in power supply ripple and droop in the situation.
Good advice.
Not trying to frighten anyone, just trying to get all the pencils parallel
before counting<G>.
Original Message
From: Allan Lane [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=0VTRWsDTP_UZqLVQEcdi4fa02Az0eIywOT_HNQFd34wpXhlo8ktwJxECon5B7L3T_ZIwfzo--2poDrznpMnbnG1g]allan.lane@h...[/url
Sent: Thursday, February 05, 2004 1:18 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Re: How would you increase current?
Solutions:
1. Use one 7805 for your BS2 current, and a
separate one for the 'high-current' line. DON'T
connect the two +5 volt lines together. DO connect
both grounds together. DO use capacitors to
provide clean power to the BS2.
2. Use one TO-3 can LM338 adjustable regulator,
good to 5 amps, supporting current pulses to
7 amps.
--- In basicstamps@yahoogroups.com, "lanceallenr" <lanceallenr@y...>
wrote:
> I am building a project with my basic stamp. I will use a ua7805
> voltage regulator. The regulator only puts out 1.5 Amps and I need
> 2 Amps to drive my high-current circuit. Can I simply put two
> ua7805's in parallel. Or is there another way of doing this. I am
> using a 12 Vdc 7A battery.
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
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shut down if shorted to ground. At those current levels, you'll probably need to
use heatsinks depending the duty cycle. Also keep the input to the regulator as
low as practical to reduce the power dissipated as heat in the regulator.
lanceallenr <lanceallenr@y...> wrote:I am building a project with my basic
stamp. I will use a ua7805
voltage regulator. The regulator only puts out 1.5 Amps and I need
2 Amps to drive my high-current circuit. Can I simply put two
ua7805's in parallel. Or is there another way of doing this. I am
using a 12 Vdc 7A battery.
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject and Body of
the message will be ignored.
Yahoo! Groups Links
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[noparse][[/noparse]Non-text portions of this message have been removed]