--- In
Homebrew_PCBs@yahoogroups.com, "kaytea2k" <kaytea2k@y...>
wrote:
> I don't know what the problem is but I know that the design is
> sound. I have experience with design from the number of
> electrical/electronic engineering courses I took in college.
Though
> EE is not my major I understand the components and how they work.
> The schematic posted @ sanisis.netfirms.com is a schematic I redid
> inorder to make it easier for a fabricator.
>
> I have gone over the schematic here with some professional
> fabricators and I am HERE trying to get you all to help. Any
poster
> should know that a schematic should be tested and working. I
believe
> once I have a layout and prototyped board then there should be no
> problem as far as adding and removing.
>
> If you have any constructive suggestions or are able to DO the work
> then please reply to my e:mail. kaytea2k@y...
>
> Karega
Please don't take our conversation as criticism. If you review the
posts, we chat about things all the time and stray from the topic
with a little energy to keeping it generally about electronics and
making boards.
The schematic is a very general outline.
http://sanisis.netfirms.com/The are no notations on the caps on the power supply. probably
0.01uf or 0.1uf,
all resistors could be 1/4 watt
no spec for the diode
RX433 is not a standard part, but a part in kit form. there are a
few variations on that part.
No antenna connection device is listed.
The 555 capacitor is not listed for pin spacing, it could be 100 mil
or 400 mil as different caps have hugely different pin spacing.
The transistors for the LEDs are not called out, they are probably
TO92 case, but are the EBC, BCE, ??
Power connections are not called out, are they solder pads for wires
or spacing for screw terminals or pins for a Molex or other ?
if screw terminals, are they 100mil ? 3.5mm ? 5 mm ? 5.09mm ? 3/8
inch?
A lot of people tie MCLR to Vcc with a 4.7k or 10k and not 100k to
ground.
There is no ISCP listed, so the PIC would need to be pulled for
programming.
I'm not saying that we can't do such a board, but that with roughly
140 holes there would be 20 mil for resistors and caps, 29 for the
DIPs, something for the connectors, and something for the antenna.
The only way most of us would consider making such a board is if we
had all the parts to measure or if all the parts were fully listed on
the schematic.
For example, I just made a board for a customer and the manufacture
of the switches gave me physical dimmentions for the pins and
electrical connections. Only problem is that the information was
wrong. on a switch pins 1 and 3 were common when pins 1 and 2 were
listed as common. instant short. required modification of the
board. Luckily, the customer gave me the data from the
manufacturer. Customers are sooo much more understanding when they
make the mistakes.
It may be a simple matter to download ExpressPCB and use that free
layout software, or WinQCad as that is free and has a very shallow
learning curve.
Please understand that making a board requires multiple layers.
The most general is done, your schematic.
next is parts selection followed by the math for verification that
the ranges are compatible.
Next is re-selection of parts as needed followed by manufacture or
supplier part numbers.
that is followed by package physical dimensions, hole sizes, pin
spacing clearance around parts for heat, ventilation, connection,
clearance etc.
then the board can be laid out with hopes that there are no
mistakes. A TO-92 BEC may be purchased when a EBC was laid out.
requires some attention when stuffing the board. ie: my switch
problem.
Then of course, there is the final step of making sure it will fit an
enclosure or housing, and that it has holes for mounting.
I didn't take the time to write this to make fun, but to try to
convey that it looks really really simple, but this is one area of
endeavors where the devil is in the details.
Electrical spec details
connection details
physical layout details
and physical properties details.
All those have to be 100% compatible or the thing won't work.
I listed enough questions that would prevent me from making such a
board from this schematic and I bypassed some of the more obvious
ones in case others want to point out some of the missed requirements.
But, I can say with total certainty, that the board as laid out with
the parts listed in the schematic will not work. There is at least
one flaw that will prevent proper operation.
Dave