Tom Del Rosso wrote:
Ian Field wrote:

And political rants - its got so bad, even I've taken the attitude;
"when in Rome do as Romans" once or twice.

A binaries group dedicated to schematics should be something really
special - I don't think it ever fully lived up to that, but in the
past few years its been dragged down into the sludge.

And when you started a political thing it wasn't a bad thing. I like
them for the view into UK politics. It doesn't matter if I agree.

It was never very convenient to make gifs of schematics. Most people
don't seem to have CAD readily at hand.

There are a number of free/cheap schematic drawing programs: Eagle
and Express PCB for example.
Nothing wrong with ASCII art.
Here is an example copied from years ago:
James Arthur wrote:
Robert Baer wrote:

Robert Baer wrote:




150K 120K
+-----/\/\----+-----/\/\--+---
| | |
| | |/------+
--- +--------+---| 2N2369A
- | | |\
| C1 --- V
| 330p --- |
| | |
Cld --- +-----+
22p --- | |
| C2 --- \
o 250p --- / 4.3K
Xtal | \
o | |
| | |
| | |
+--------+-----+
|
---
-


With C2 at 330pF, only the 200Khz tuning-fork crystal oscillates,
and only with a supply voltage near 2.5V; At 3V to 20V supply,
2Mhz-10Mhx crystals work and the 12Mhz does not.
With C2 at 250pF, no tuning-fork crystal will oscillate, and
those from 2Mhz to 12Mhz does.
However, the higher frequency crystals oscillate at a lower
amplitude with a given supply voltage.
This circuit gave me a surprise; it is clear at 2Mhz, that it
operates as a class C circuit from about 5V up.
Put a 50 ohm resistor in the collector and pick off the signal
with virtually zero disturbance of the oscillator.

I have done some fiddling with C1 and C2 and have been unable to
get the other tuning-fork crystals to work.
Any suggestions?



Crystal properties vary widely depending on cut, frequency,
and mode, which is why there are so many different circuits.

Those tuning fork crystals have big ESRs, like 30-50k
@ 32KHz, dropping as frequency rises.

I'd think a JFET-based Pierce, having a high-Z input,
could be the ticket for the high-ESR types. There's
one in the National FET Applications that went
something like this:

Vdd
-+-
|
|
.-.
| | R1
| |
XTAL '-'
_ C1 |
| | || |
.--|| ||---||--+
| |_| || |
| |
| |-+
| | Q1
+-----------|-+
| |
| |
.-. ===
| | R2 GND
| | 10M
'-'
|
===
GND
(created by AACircuit v1.28.4 beta 13/12/04 www.tech-chat.de)


I once made a very nasty, ugly little 32,768 Hz tuning
fork oscillator like this (it breaks just about all the
rules--for curiosity only!)

+1.5v
-+-
|
|
.-.
.----. | | R2
| | | | 1M(?)
.-. | '-'
R1 | | | |
10M | | '----+
'-' _ |
| | | X1| (R1-2 values are guesses; I don't
+--|| ||--+ remember what I actually used)
| |_| |
| |
| |/ Q1
'-------| MSPA18
|
|
|
===
GND
(created by AACircuit v1.28.4 beta 13/12/04 www.tech-chat.de)

Neither of those shows proper crystal loading--that's
crystal-specific, and up to you.

To adapt your existing circuit use a much higher
gain transistor and increase impedances--the emitter
load resistor, and, especially, the bias resistors
(they're loading the crystal something fierce right now)
--and you might get it to oscillate.

Cheers,
James Arthur