A quick idea. Have not tried.
Input from Serial charges cap. When voltage is high enough to start pic, P1 goes high switching signal to P2. P2 receives signal. P3 sends signal. Cap would be 4700 or larger.
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Would this work?
A quick idea. Have not tried.
Input from Serial charges cap. When voltage is high enough to start pic, P1 goes high switching signal to P2. P2 receives signal. P3 sends signal. Cap would be 4700 or larger.
Dave
Always wear safety glasses while programming.
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I'd use a small battery pack rather than a cap, trickle charge the pack off the serial line when you can, diode block it so the pack can't feed back into the data line. Cap's are too unreliable in cases like this.Originally Posted by mackrackit
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You might be right about the caps being unreliable, but the current is so low on the lines it might take some time to charge the battery pack.
Question - I thought RS485 voltage was negative without a signal on the line?
My original idea came from thinking about RFID chips.
Dave
Always wear safety glasses while programming.
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If it is, then hook the battery up backwards
Seriously...I'm thinking that even a small battery with an intial charge on it would probably maintain thru the '485 line. And a '675 should be able to run on sub-milliamp current.
How often will the RX be powered, what's it's average daily 'duty cycle'?
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More fun to hook caps up backwards.
Dave
Always wear safety glasses while programming.
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Now you're speaking my language...More fun to hook caps up backwards.
I always say 'Everything comes prepackaged with a certain amount of smoke. You let that smoke out, it quits working.' (goes for cars too)
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Thanks blokes, I have found a thing called Pbus which looks promising so I'm gunna have a further look at it.
Peter Moritz.
Up the bush, Western Plains,
New South Wales,
Australia.
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