Re: power on delay using a 555 chip
- From: "Chris" <cfoley1064@xxxxxxxxx>
- Date: 18 Aug 2006 18:44:44 -0700
kfel wrote:
Chris, I did try out the circuit but went about the testing in a phased
manner.
Step 1:
I rigged up the 555 in astable mode. Provided it with supply from a 9V
battery. Checked the output pin for oscillation and found it to be ok.
Step 2:
Then I rigged up a simple DC supply circuit using a 5.2V zener in
parallel with a 470uF/16V capacitor. (This circuit is explained in the
application note 954A of microchip corporation). Using this as the
primary source of the power to the 555 i checked the output pin for
oscillations and found it to be ok.
Step 3:
Rigged up a circuit containing of a 40W GLS lamp in series with triac
BT06600 from ST Micro. Connected one end of the lamp to the MT2
terminal. Other end of the lamp was connected to Phase (240Volts AC
RMS). MT1 terminal was connected to Neutral. Connected a wire from gate
terminal but did not connect it to the output of the 555 as yet.
Step 4:
Switched on the power supply and checked the output at pin 3 of 555 and
found it to be ok. As the gate terminal was not connected the lamp did
not glow. Now when i connected the gate terminal to the output of the
timer the 555 went kaboom. So did the triac. Unable to understand what
went wrong. Any help would be appreciated.
Hi, Kfel. Sorry for your troubles.
The consensus of this group over time has been that the transformerless
power supplies shown in the Microchip appnote are not suitable for
anyone who asks for advice from this group.
Mr. Fields was kind enough to mention why your 555 blew up. Your
circuit common in Fig. 10, 11 and 12 are not at the same potential as
neutral. For Fig. 12, it's a long ways away!
I'd like to add that there are any number of other ways to do this
which don't involve putting your circuit at line voltage potential.
First, your 555 can drive a small relay directly, or it can drive an
NPN transistor which can switch the relay coil. If you're not
interested in a relay, you can use an optotriac IC to drive your triac.
If you want an authentic '70s feel to your circuit, you might have
your 555 drive the reset pin of another 555, which drives a pulse
transformer. The pulse transformer output can easily drive a sensitive
or non-sensitive gate triac or SCR.
The common element to all of these is that you're using an isolated
power source for fun and safety. A throwaway wall wart should me more
than sufficient, if you provide a voltage regulator of any kind that
can handle the current of your circuit.
If you'd like advice on any of these, feel free to ask.
Play safe, and have fun.
Chris
.
- Follow-Ups:
- Re: power on delay using a 555 chip
- From: kfel
- Re: power on delay using a 555 chip
- References:
- power on delay using a 555 chip
- From: kfel
- Re: power on delay using a 555 chip
- From: Chris
- Re: power on delay using a 555 chip
- From: kfel
- Re: power on delay using a 555 chip
- From: Chris
- Re: power on delay using a 555 chip
- From: kfel
- power on delay using a 555 chip
- Prev by Date: Re: Zero Ohms = Mathematically Incorrect
- Next by Date: Re: Can electricity flow through air w/out sparking?
- Previous by thread: Re: power on delay using a 555 chip
- Next by thread: Re: power on delay using a 555 chip
- Index(es):
Relevant Pages
|
