555 timer

hello, this may seem like a dumb question but what do you do to reset a

555 timer on pin 4? 5V, a pulse, etc ?

Thanks

Reply to
minski_wit
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Pull it low.
Reply to
John Fields

Is it also not true that it must be pulled high (or allowed to go high) at the end of the reset interval, before the timing cycle will start?

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- this is the CMOS version; does anyone use bipolar 555s any more?

Thanks, Rich

Reply to
Rich Grise

A good solution is :

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Fero

Reply to
Fero

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For the device the OP asked about, the 555, releasing the low on the
RESET- input will be sufficient to enable the chip.  Whether the
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Reply to
John Fields

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From:

http://groups.google.com/support/bin/answer.py?answer=12348&topic=250
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Reply to
John Fields

The drive current is a bit higher for the bipolar version, some of the CMOS types won't handle as much supply voltage.

AFAIR, everything else is better on the CMOS- 100kHZ is getting to the limit for the bipolar type, but some of the CMOS ones will do MHz. With CMOS, swing is to the rails, no big spikes of current, no bias current to speak of.

Best regards, Spehro Pefhany

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"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
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Reply to
Spehro Pefhany

Seconded. I don't use bipolars anymore at all. ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

Thanks, George H. vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv

The bipolar 555/556 gives up the ghost at around 200kHz, years ago I kit built a TV pattern generator with 555 sync generators - the 15.625kHz line timebase 555 proved impossible to calibrate, it was pretty flaky and wouldn't stay set.

The bipolar 555 won't be any good as a stable frequency generator at 100kHz, the CMOS version is claimed to be good upto about 2MHz but has rather limited O/P drive capability.

Reply to
Ian Field

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Back in college the final project in a course was to build something. I made this bike speedometer/odometer (magent on wheel and reed realy.) I used a 555 for timing and the tempco of the carbon comp resistors I used killed the stability. But I only learn by making mistakes..... In this case I don't care if the frequency drifts around a bit.

George H.

Hz,

Reply to
George Herold

Years ago I too did a project using a 555 and it would drift a bit depending on what you're doing.. So, I had some ovens laying around that worked perfectly :).

P.S. choice of R's and Caps also makes a difference.. You can also bond a diode on the case of the chip to be used to help counter act thermo issues.

Jamie

Reply to
Jamie

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