gnupic: Re: [gnupic] Line recievers
Subject:
Re: [gnupic] Line recievers
From:
"John Woolsey" ####@####.####
Date:
25 Oct 2006 19:15:17 +0100
Message-Id: <200610251116.AA190185656@Activation.net>
I did a google on this and I don't understand it really. What exact circuit do I hook up? What happens if I run a 43V+ to the pin diode do I fry my microcontroller?
- bfn - JAW
---------- Original Message ----------------------------------
From: Dan Andersson ####@####.####
Reply-To: ####@####.####
Date: Wed, 25 Oct 2006 19:00:27 +0100
>Why even use a chip?
>
>Use pin diode(s) instead. They are easy to control and are surprisingly simple
>to drive. Most cheap pin diodes give you switch times n the GHz region so I
>wouldn't worry about the speed and also, more important, the footprint for a
>diode and the corresponding resistor is so small.
>
>//Dan, M0DFI
>
>
>
>
>On Wednesday 25 October 2006 18:42, 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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>--
>Dan Andersson, M0DFI
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