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555 timer IC toys for children with disabilities

M

mark3

Jan 1, 1970
0
Hi, can any one help?
I,m just teaching myself basic electronics and have
built a hobby kit (9V) using a 555 timer to tigger a LED off/on over
various lengths of time. Have run a lead from pin 3 of 555 timer IC
to base of transistor (548) to trigger 9v electric motor without
success,I have also tried using a 9v relay but again not enough power
to drive electric motor. My aim is to set up various tigger switchers
with timming cicuits to drive different toys and lights to help
stimulate learning for a child with intellectual dissabilities. If any
one could offer some advise and/or some easy to read circuit diagram's
in this area it would be greatly appreciated.


Thankyou

Mark3
 
J

Jason

Jan 1, 1970
0
Instead of using a 548 NPN device, perhaps you should try using a
MOSFET. Bipolar transistors act as a "switch" for current input and
the maximum output current of the 555 timer (~1mA) will limit the
current that your 548 can draw from your battery. If you switch this
to a (high-power?) FET, you will be able to set your own limits within
your range by picking the right device. FETs work off of the voltage
levels applied to the gate and you don't have to worry about current
limitations of the 555 timer.

This, of course, is all assuming that you've hooked up everything
correctly and it is a problem with the 548 transister's capabilities.

gl,

Jay
 
P

PeteG

Jan 1, 1970
0
A 555 timer can source/sink ~200mA so not only could it drive a small relay
directly it has no problem driving BC548 or a power darlington transistor.
You should check the manufacturers data sheet for the actual 555 timer you
are using. The CMOS versions of this chip have lower output ratings.

Here's a couple of links to show you the way, and if you Google for 555
timer circuits you'll find a shed load of info'

http://www.cpemma.co.uk/555pwm.html
http://www1.jaycar.com.au/images_uploaded/relaydrv.pdf

Pete
 
S

Stefaan Vanheesbeke

Jan 1, 1970
0
What do you mean with not enough power??

Is the battery going down, or is the driving system not ok?
 
B

Bob Monsen

Jan 1, 1970
0
Hi, can any one help?
I,m just teaching myself basic electronics and have
built a hobby kit (9V) using a 555 timer to tigger a LED off/on over
various lengths of time. Have run a lead from pin 3 of 555 timer IC
to base of transistor (548) to trigger 9v electric motor without
success,I have also tried using a 9v relay but again not enough power
to drive electric motor. My aim is to set up various tigger switchers
with timming cicuits to drive different toys and lights to help
stimulate learning for a child with intellectual dissabilities. If any
one could offer some advise and/or some easy to read circuit diagram's
in this area it would be greatly appreciated.

If you have an extra NPN transistor, try this:

View circuit using 'courier' or other fixed space font:


9V -------------o---- MOTOR + terminal
|
-
^
|
.---o---- MOTOR - terminal
| |
|/ |
PIN3-[1k]--| |
|> |
| |
| |/
'-|
|>
|
|
GND--------------'

This is called a 'darlington' configuration, and it boosts the output
with a wimpy input.

Also, use a 1uF and a 0.01uF cap across the Vcc and Vdd inputs of the
555, or the voltage drop when the battery turns on may retrigger the
timer. Even better, use a separate battery, and connect the grounds.

The diode protects your transistors.

---
Regards,
Bob Monsen

Mathematics is nothing more, nothing less, than the exact part of our
thinking.
- Luitzen Brouwer
 
M

mark3

Jan 1, 1970
0
Hi jay
Thankyou for your time and help

Kind regards
Mark
 
M

mark3

Jan 1, 1970
0
Hi jay
Thankyou for your time and help

Kind regards
Mark
 
M

mark3

Jan 1, 1970
0
Hi Pete
Thankyou for your time and help. The web sites are very useful !

Kind regards
Mark
 
M

mark3

Jan 1, 1970
0
Hi Pete
Thankyou for your time and help. The web sites are very useful !

Kind regards
Mark
 
M

mark3

Jan 1, 1970
0
Hi Bob
Thankyou for your time and help

Kind regards
Mark
 
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