Homebrew PCBs

Leon Heller wrote:

>----- Original Message ----- 
>From: "Dave Mucha" <dave_mucha@...>
>To: <Homebrew_PCBs@yahoogroups.com>
>Sent: Saturday, May 22, 2004 7:39 PM
>Subject: [Homebrew_PCBs] Re: New file uploaded to Homebrew_PCBs
>
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>>Good thing you fixed the crystal.  That was required to make it work
>>and too simple of a mistake.
>>
>>A question is why the diode on MCLR ?
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>Possibly to discharge the capacitor that is often used on MCLR when power is
>removed. However, there is no capacitor. 8-)
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>>Another question is why all the shift registers to only light a few
>>LED's ?  And why the transistor on the LED's ?  The shift register
>>can handle 20mA in a drain mode, and each LED can be run at 10mA so
>>there are lots of unneeded parts.  OR... more likely many more parts
>>that are not shown.
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>Perhaps the SRs are to minimise the number of outputs from the PIC, enabling
>more LEDs to be added without taking up more pins.
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It looks like it can have three different outputs going at the same 
time, each with two led's. The schematic shows PNP transistors for the 
led driver, I think they should be NPN, though.

The shift registers are all clocked by the same 555 timer (40KHz ?) 
maybe so the on/off times are consistent.

A wireless receiver that can be told to send unique commands to three 
other things?

mickeym