Science fair project
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Hi All
My 13 year old son is getting ready for next years science fair at his school. He wants to show how electronics have evolved over the years. But he needs your help. Dose anyone know of a schematic of the internals of a 555 timer? He is going to make a simple flasher circuit with it, and he wants to show how small electronics have become by making one circuit using the 555, and one with the transistor, resistor equivalent of the 555.
Thanks
TC & TC jr.
My 13 year old son is getting ready for next years science fair at his school. He wants to show how electronics have evolved over the years. But he needs your help. Dose anyone know of a schematic of the internals of a 555 timer? He is going to make a simple flasher circuit with it, and he wants to show how small electronics have become by making one circuit using the 555, and one with the transistor, resistor equivalent of the 555.
Thanks
TC & TC jr.
Comments
>Hi All
>
>My 13 year old son is getting ready for next years science fair at his
>school. He wants to show how electronics have evolved over the years. But
>he needs your help. Dose anyone know of a schematic of the internals of a
>555 timer? He is going to make a simple flasher circuit with it, and he
>wants to show how small electronics have become by making one circuit
>using the 555, and one with the transistor, resistor equivalent of the 555.
>
>Thanks
>
>TC & TC jr.
You may want to check out this web site. It's all about the 555 timer.
http://www.andy-clarkson.co.uk/555/
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Original Message
From: Anthony Conti [noparse][[/noparse]mailto:aconti@neo.rr.com]
Sent: Friday, June 15, 2001 2:22 PM
To: basic stamp
Subject: [noparse][[/noparse]basicstamps] Science fair project
Hi All
My 13 year old son is getting ready for next years science fair at his school. He wants to show how electronics have evolved over the years. But he needs your help. Dose anyone know of a schematic of the internals of a 555 timer? He is going to make a simple flasher circuit with it, and he wants to show how small electronics have become by making one circuit using the 555, and one with the transistor, resistor equivalent of the 555.
Thanks
TC & TC jr.
To UNSUBSCRIBE, just send mail to:
· basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed with.· Text in the Subject and Body of the message will be ignored.
Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
--- In basicstamps@y..., "Chris Loiacono (E-mail)" <chris01@t...>
wrote:
> Try this pdf file:
>Hi All
>
>My 13 year old son is getting ready for next years science fair at his
>school. He wants to show how electronics have evolved over the years. But
>he needs your help. Dose anyone know of a schematic of the internals of a
>555 timer? He is going to make a simple flasher circuit with it, and he
>wants to show how small electronics have become by making one circuit
>using the 555, and one with the transistor, resistor equivalent of the 555.
>
>Thanks
>
>TC & TC jr.
Fun project! Take a look at this Datasheet...
http://www.national.com/ds/LM/LM555.pdf
...One thing to keep in mind with this schematic...
Q5, Q6, and Q22 are actually two transistors...
ie:
Type:
Q5, Q6, Q22 - Base and Emitter are shared with two seperate Collectors.
The Following Transistors must be well matched:
Q12 & Q13
Q15 & Q16
Base = straight leg
Collector = bent leg
Emitter = bent leg with arrow
NPN = arrow going out
PNP = arrow going in
Beau Schwabe IC Mask Designer
National Semiconductor Wired Communications Division
500 Pinnacle Court, Suite 525 Mail Stop GA1 Norcross, GA 30071
--- "Chris Loiacono (E-mail)"
<chris01@t...> wrote:
> Try this pdf file:
>
Original Message
> From: Anthony Conti [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=fVawx5nXpGBE3mKcUcmS7zlaRDH8WW_qHoSGqEiZcpOwlTQd77TdTtFU0PU86Na3IaXIxHLSHg]aconti@n...[/url
> Sent: Friday, June 15, 2001 2:22 PM
> To: basic stamp
> Subject: [noparse][[/noparse]basicstamps] Science fair project
>
>
> Hi All
>
> My 13 year old son is getting ready for next years
> science fair at his
> school. He wants to show how electronics have
> evolved over the years. But he
> needs your help. Dose anyone know of a schematic of
> the internals of a 555
> timer? He is going to make a simple flasher circuit
> with it, and he wants to
> show how small electronics have become by making one
> circuit using the 555,
> and one with the transistor, resistor equivalent of
> the 555.
>
> Thanks
>
> TC & TC jr.
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed
> with. Text in the Subject
> and Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to the Yahoo!
> Terms of Service.
>
>
> ATTACHMENT part 2 application/pdf name=555.pdf
__________________________________________________
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>What are Q5,Q6,and Q22? can he use common NPN & PNP trans?
In this case those are ALL PNP's, but in answer to your question...
yes!
If you took 2 PNP transistors and connected the BASE's together, and
you also connected the EMITTER's together, while leaving the COLLECTORs
alone, you have essentially "made" the transistor represented in the
schematic for Q5, Q6, and Q22.
The included GIF shows two equivalent schematics
A couple of suggestions for the 555 timer project:
1) Look into the ARRL Radio Amateur Handbook for information.
2) Signetics was the original designer and manufacturer of the device. It
has since been copied and somewhat improved over the original by many, many
other manufacturers including low power CMOS versions.
3) Look into old & back issues of "Popular Electronics" magazine for 555
timer projects and a simplified explanation of it's workings.
4) Do search the web for "NE-555", "NE555", and other variations on the
nomenclature for additional information. I did this several months ago and
found a significant amount of information.
5) Check out the Motorola Semiconductor (now ON Semiconductor), National
Semiconductor, Phillips Semiconductor, and Texas Instruments data sheets and
linear handbooks for information.
6) From what I remember, the inside workings are basically a resistive
voltage divider of 3 equal value resistors, two voltage comparators, a RS
flip flop, an uncommitted open collector NPN transistor driven by the
internals with it's emitter grounded and a few other bits and pieces.
7) The 555 timer has been and continues to be very successful.
8) Perhaps you come up with a new design !!!!!
Wondering where you are located?
Best wishes on your project.
Burt Schultz
Another thing your son should be aware of is that the design of
integrated circuits is quite different from discrete circuits. Beau
alluded to that when he pointed out the double collector transistors,
and that some of the transistors in the circuit have to be well
matched by pairs.
In the design of discrete circuits it is possible to use precision
resistors and stable high value (~0.01 uf) capacitors. But discrete
transistors will rarely match well, especially when they are at even
the slightly different temperatures that come from being in separate
packages.
On the other hand, fabrication integrated circuits easily gets
transistors that are very closely matched in their base and gain
curves. Since they are on the same chip, they will also be at pretty
much the same temperature. And while it is quite easy to make two
resistors _equal_ in value, it is very difficult to control their
_absolute_ value or even their linearity (the current is not a good
linear function of the voltage). Capacitors of more than a few
picofarads are also impractical. All this comes from having the
circuit fabricated on one chip of silicon. Integrated circuits
depend heavily on the superb matching of transistors, and resistors,
and de-emphasises the horrific absolute values.
Discrete design does not translate easily to an integrated circuit,
and vice versa, it is hard to take an integrated circuit and
implement it as is in discretes.
To match transistors by pairs, you need to measure their forward base
emitter voltage at a certain temperature (not just after pinching
them with your fingers!), and also the forward gain. When you find
the closest match you can in a pile of transistors, then you glue
them together so that they will always operate at the same
temperature. It can be done.
A compromise is the use of transistor arrays, which consist of a
bunch of transistors fabricated on one chip so they match very well,
just like the transistors in ICs. An example is the CA3096, which
contains 3 NPN and 2 PNP in one 16 pin dip package. Or the CA3084,
which has 6 PNPs in a 14 pin dip, with 4 of them hooked up as current
mirrors (which is what you are making with the dual collector Q5 and
Q6 that Beau described in the '555 circuit). A great beginner's book
on the ideas behind integrated circuit design is "IC Array Cookbook"
by Walter Jung. Unfortunately, I think it is out of print. It is
well worth having if you want to get into the ideas behind IC design
and how it differs from discrete design. If your son wanted to use
IC arrays, it would still take a several of them to implement the
"semi-discrete" '555 timer. But at least he wouldn't have to sort
through piles of discrete transistors to come up with sort-of matches.
Good luck Jr.--it sounds like a great project!
-- regards,
Tracy Allen
electronically monitored ecosystems
mailto:tracy@e...
http://www.emesystems.com
>At 02:22 PM 6/15/01 -0400, you wrote:
> >Hi All
> >
> >My 13 year old son is getting ready for next years science fair at his
> >school. He wants to show how electronics have evolved over the years. But
> >he needs your help. Dose anyone know of a schematic of the internals of a
> >555 timer? He is going to make a simple flasher circuit with it, and he
> >wants to show how small electronics have become by making one circuit
> >using the 555, and one with the transistor, resistor equivalent of the 555.
> >
> >Thanks
> >
> >TC & TC jr.
>
>Fun project! Take a look at this Datasheet...
>
>http://www.national.com/ds/LM/LM555.pdf
>
>
>...One thing to keep in mind with this schematic...
>
>Q5, Q6, and Q22 are actually two transistors...
>
>ie:
>
>Type:
>Q5, Q6, Q22 - Base and Emitter are shared with two seperate Collectors.
>
>The Following Transistors must be well matched:
>Q12 & Q13
>Q15 & Q16
>
>Base = straight leg
>Collector = bent leg
>Emitter = bent leg with arrow
>
>NPN = arrow going out
>PNP = arrow going in
>
>
>
>
>Beau Schwabe IC Mask Designer
>National Semiconductor Wired Communications Division
>500 Pinnacle Court, Suite 525 Mail Stop GA1 Norcross, GA 30071
>