gnupic: Re: [gnupic] Line recievers
Subject:
Re: [gnupic] Line recievers
From:
Julian Green ####@####.####
Date:
26 Oct 2006 08:29:54 +0100
Message-Id: <20061026072330.L59592-100000@pschulz.london.corp.yahoo.com>
You could just try using a high ohm resistor. Somethign like 100k. I have
seen an application note on the microchip web site that monitors the zero
crossing point in an AC waveform by connecting directly to mains supply.
There are protection diodes on every input of a PIC and provided you dont
exceed the input current no damage results.
Provided the output of your switch goes to zero volts the resistor will
work fine.
Julian
On Wed, 25 Oct 2006, John Woolsey wrote:
> The application is an input switch within a pinball machine. The reason for the high voltage is to ensure that there is not interpherence. Reaction time within 100 ms would be acceptable. All of the microswitches are depressed for longer periods of time than that.
>
> The leading microcontroller to use is a PIC18F2450. 8 of the pins would be configured for input. 1 to a pot for configuration (A/D conversion gives me the ability to adjust the input number.) And the remaining (14) for output.
>
> I want to wire a 24v supply to microswitch to a line receiver that outputs a TTL output to my microcontroller input. This seems the standard pinball way to do input. They question is what chip do I use?
>
> - thanx - JAW
>
>
>
>
> ---------- Original Message ----------------------------------
> From: Arnim Littek ####@####.####
> Reply-To: ####@####.####
> Date: Wed, 25 Oct 2006 20:31:48 +1300
> >On Wednesday 25 October 2006 18:58, John Woolsey wrote:
> >> I am trying to build a 24 volt micro switch circuit to a ttl input
> >> switch on a pic micro controller. I was told to use a line receiver. But
> >> everything I look at seems to be a high voltage rs-232 that goes
> >> positive and negative. I just want a +24V line through a switch into a
> >> line receiver. What chip should I use?
> >
> >If you want TTL input, then you want high above 2.0V and low below 0.8V on the
> >micro, is that correct?
> >
> >You don't say what switch levels you expect to tolerate on the 24V side. How
> >noisy is your 24V cct? Is the switch debounced?
> >
> >How fast do you want the reaction? If you're just detecting a level change
> >with no speed considerations, a resistive split with a small capacitor on the
> >bottom resistor is fine. If your 24V line is really noisy, prone to spikes,
> >then you might want to protect your comparator-with-hysteresis.
> >
> >Lots more information required in order to come up with something like an
> >optimal solution.
> >
> >FWIW,
> >
> >Arnim
> >
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