Re: Please suggest a time delay toggle switch

On 7 Sep 2005 20:26:36 -0700, mingyan_chow@xxxxxxxxxxxx wrote:

>John, I'd very much appreciate your design. That is certainly a
>professional design. In your circuit diagram, U3 is a dual oscillators
>for 33 and 45. U1 is for power on reset status.

---
No, U1 is the toggle. On power-up C5R2 resets it which disables the
oscillators and sets the latch (U2C and D) to select the 33 RPM
oscillator. Thereafter, a short press on the switch will enable the
oscillators and send out the signal for 33RPM, and the next press
will disable the oscillators and place the circuit in the power-up
state. If a long press is made, the oscillators will be enabled but
the 45 RPM signal will be output and, if the switch is pressed after
that the oscillators will be disbled and the circuit will be
returned to the power-up state. One thing I didn't put on the
schematic but which you may want to consider doing would be to
connect a high efficiency LED to U2-4, like this:


U2-4>---+
|
[1k5]
|
[HLMP4700]
|K
GND>----+

What that will do is allow you to see when the circuit is ready to
switch to 45, (when the LED lights up) and when you release the
button after that the circuit will output the 45 RPM clock and the
LED will go out.


---

>U2 AB is the time dealy
>switch. U2 CD is a toggle switch.

---
No, U2CD is a latch used to select the 33 or 45 clock as the output.
---

>U4 ensure there is only one clock
>signal will be pass to output. Am I right? Excellent. This circuit is
>very useful for me.
>Please forgive me raising some new issues. As I digging deeper, more
>questions is beuing raised. Both 33 and 45 ouput signals need to be
>adjusted to a certain level. Therefore, 33 and 45 clock signal has to
>be rectified and go through a variable pot .I found the original
>circuit has a output of 1V P to P rectified signal feed to the voltge
>follower. In this case, U4 gate may not be approriate.

---
The output from U4-11 will vary from about zero volts to Vcc, so
it's already "rectified" in that it never goes below ground. If you
need to attenuate the output, an easy way is to connect a pot from
U4-11 to ground and to take the output from the wiper. If you need
more current than CMOS can provide you can follow the output with an
LM324 wired as a unity-gain buffer.

--
John Fields
Professional Circuit Designer
.

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