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Science Forum Index » Electronics - Basics Forum » Timer circuit
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| Author |
Message |
| P.Webb |
 Posted: Thu Jan 25, 2007 4:32 pm |
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Guest
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Hi All,
I want to make a time delay circuit using transistors,
12v supply switch on a 3Watt bulb and go off after about 3 seconds
if possible, I don't want to use a relay or 555
and I would like to use pnp ZTX 751 transistors which I have plenty of !
Thanks.....Peter |
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| Jonathan Kirwan |
| Posted: Thu Jan 25, 2007 6:41 pm |
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Guest
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On Thu, 25 Jan 2007 20:32:45 -0000, "P.Webb" <cartronics@yahoo.com>
wrote:
Quote: I want to make a time delay circuit using transistors,
12v supply switch on a 3Watt bulb and go off after about 3 seconds
if possible, I don't want to use a relay or 555
and I would like to use pnp ZTX 751 transistors which I have plenty of !
Peter, since I recently posted something close to what you want, I'd
like to save time and suggest that you might try something like the
following:
Quote: : +12V +12V +12V +12V
: | | | |
: | | | | Momentary
: | \ | | Pushbutton
: | / R1 | O S1
: | \ 33k | \
: | / | \
: | | | \
: D2 | | | O
: 1N4148 _|_ | |<e Q1 |
: /_\ +--------| ZTX751 |
: | | |\c PNP |
: | | | |
: | \ | |
: | / R2 +----------------+
: | \ 3.3k | |
: | / --- C1 |
: | | --- 0.47uF \
: | | | / 3W
: | | | \ LAMP
: | | | /
: +---------------+ |
: | | +------, |
: | | | | D1 |
: | | | | 1N4148 |
: | ||' M1 \ _|_ |
: | ||< BSS145 / /_\ |
: '--'|, \ | |
: | R3 / | |
: | 4.7M | | |
: | | | |
: gnd gnd gnd gnd
I haven't looked at the data sheet for the Zetex part, though. I'm
assuming that you already know it can handle the 3W load.
Jon |
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