Electronics Forum / Basics / August 2006

I have seen different site using 556 set up as one timer in astable
controlling a second timer in monostable mode. Other sites show PWM by
using only one 555 timer set up in astable mode. I would really rather
use only one 555 timer, but what is the upside to using a setup with a

What kind of component would be used to indicate the presence of a load
on a residential power point (240V/10-20A) and translate the presence
of the load as
a signal to a PIC (3.5-5V) on a PCB.

I'm wondering where to find a foot controlled throttle to put on the
front of a skateboard/powerboard (or whatever you want to call it).
I'll use an electric scooter motor and controller, so I guess it
should be 10K ohms. I've heard of rotary tool speed controllers

What will you see if u measure a sensitive Voltmeter to the end leads
of a Diode ?

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Is this correct?
Thank you,
Christopher Lusardi

There must be a million of these posts on this group and I apologize in
advance if I'm violating some rule.
I come from a computer science background and I'm now looking to get
into electronics as a hobby.  I have a few ideas for circuits I'd like

I saw many companies use different names. What are the differences
between those two: Motor Drivers & Motor Controllers? Thanks.

I have a question about motor drivers/speed controllers. Where do you
find out the info on how many motors can be controlled?
http://newark.com/NewarkWebCommerce/newark/en_US/endecaSearch/searchPage2.jsp ...

I'm thinking of making a small hotplate for the purpose of heating PCB
etchant, and possibly to keep the tank up to temperature while etching. At
the low end of the temperature range, it should be able to maintain 50degC
max. Being able to go hotter and boil stuff, etc, would be ...

What is a DC motor speed controller?
I'm talking about DC motors like they use for electric scooters in
the 250 W to 500 W range.
Ordinarily, can I just connect a battery through a switch to the

the 2N4921 does not seem to have its Rja published anywhere.  what
would be a safe figure to use?  my guess is 125 deg C/W with 1 W Pd.  i
found that somewhere on a TO-225 transistor, the 2n4921 is TO-126 (if
there is a difference.)

ok, thank you all for your help.  I just bought a brand new 555 IC,
plugged it in, and still this thing doesn't work.  the capacitor
polarity is correct, the LED polarities are correct (and they are in
working order) ... what is the problem here?

I have recently installed an outside light which is switched usind a
pir, however I want to install a second pir at the other end of my
garden to also switch the same light on when movement is detected. the
second pir has a power supply right next to it so I was wondering can I

I need to be able to send and recieve data from a custom electronic
board to my computer program (written in c). from what i've researched
so far i need a UART chip. Is this true?
The device that im making will have a high(on) or low(off) state, there