1. Home
  2. Electronics Design
  3. Pull-down

Pull-down

Hello,

I sincerely apologise for the phenomenally newbie question but here goes....

I have an ISD1730 chip which essentially plays a sound thru a speaker whenever one of the pins drops low, it has an internal pull up resistor. How can I use a non-physical switch to trip it? Basically I would like to have an Astable circuit trip it. How can I do this? Can I just put the output of an Astable onto it; or would I have to put a NOT gate in between so it is always high then goes low on the high pulse from the astable???

Please help

--------------= Posted using GrabIt =----------------

------= Binary Usenet downloading made easy =---------

-= Get GrabIt for free from

formatting link
=-

Reply to
James Cranfield
Loading thread data ...

one of the pins drops low, it has an internal pull up resistor.

have an Astable circuit trip it. How can I do this? Can I just put the output of an Astable onto it; or would I have to put a NOT gate in between so it is always high then goes low on the high pulse from the astable???

Need a little more information.

If your npot using a "switch", what are you using ??

An opto-isolator would work if I know what was controlling the opto.

Help me, help you !

Reply to
Donald

The latter, I think.

Reply to
mc 

--
You could use an astable with complementary outputs and drive the
1730 with the negative-true output, or if you wanted to use
something like a 555/7555 you could do this: (View in Courier)

                                IDS
                               1730
                              +----+ 
                              |_   | 
                         +---O|E   |
                         |    |    |
                         C    +----+
ASTABLE OUT>---[1KR]---B  2N3904
                         E
                         |
                        GND
Reply to
John Fields

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.