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RE: [AVR-Chat] controlling relays and motors

RE: [AVR-Chat] controlling relays and motors

2004-11-26 by David Jones

>>> wbounce@safeplace.net 26/11/2004 2:39:20 pm >>>
>I agree with the CLEAN 5V but you do not need 2 sources. You can use
the
>same source for motor and MCU. You need to put a separate voltage
>regulator on the MCU circuit from the motor circuit with caps going
from
>the input to ground and from the output to ground. 
>Also an important consideration is the type of voltage regulator you
are
>using. If it is a 7805 you need something like 1.5 volts above the
>output which over 6.5 volts. This means you can not use 4 AA
batteries.
>Six AA 1.5 V batteries will give you plenty of room but 6 AA
>rechargeables only have 1.2V which is still borderline.

In this situation you would use a low-dropout version of the 7805 as
standard practice.
What out though, LDO regs are unstable, they must be bypassed
properly.

Dave :)

[AVR-Chat] controlling relays and motors

2004-11-26 by techy fellow

As I am new to electronics, it would be of great help to me if you could let me know some of the low drop-out version of the 7805 ? For eg., brand name and/ or model reference.
 
I bought a bunch of 7805s (all in one small plastic bag) which I noticed some has different model reference. For eg. some have 7805 while others have, 7805L. I would think the latter is low drop-out type. I just want to be sure.
 
If normal 7805 requires an extra 1.5V from the source then, what extra voltage is required for the low drop-out version ?
 
Thanks in advance for the help.
cheers,


David Jones <david.jones@sercel.com.au> wrote:
>>> wbounce@safeplace.net 26/11/2004 2:39:20 pm >>>
>I agree with the CLEAN 5V but you do not need 2 sources. You can use
the
>same source for motor and MCU. You need to put a separate voltage
>regulator on the MCU circuit from the motor circuit with caps going
from
>the input to ground and from the output to ground. 
>Also an important consideration is the type of voltage regulator you
are
>using. If it is a 7805 you need something like 1.5 volts above the
>output which over 6.5 volts. This means you can not use 4 AA
batteries.
>Six AA 1.5 V batteries will give you plenty of room but 6 AA
>rechargeables only have 1.2V which is still borderline.

In this situation you would use a low-dropout version of the 7805 as
standard practice.
What out though, LDO regs are unstable, they must be bypassed
properly.

Dave :)


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