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CCS Addict
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| Electronics Question... |
 Posted: Fri Feb 24, 2006 9:38 pm |
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Guys I a looking for a circuit that can perform the following,,,
When PIC output is High (5V) it will go thru the circuit and the circuit will output (5V)
When PIC output is Low (0V) it will go thru the circuit and the circuit will output (-5V) instead of 0 V
any recomendation?? |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Fri Feb 24, 2006 10:36 pm |
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Do you want this exact thing, or do you really want an RS-232
level translator ? |
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CCS ADDict
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| Posted: Fri Feb 24, 2006 10:56 pm |
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I want to generator a sequence using PIC....
like from PIN A0...
5V -5V 5V 5V -5V -5V 5V 5V 5V -5V -5V -5V with 1 sec delay in between.
To produce 5 V,,, I can easily just OUTPUT_High(PIN_A0)....
but to produce -5 V,,, PIC can't do that...right?
so I need additional external circuit/IC to produce -5V...may I know how can I achieve that? |
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kender
Joined: 09 Aug 2004
Posts: 768
Location: Silicon Valley
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| Posted: Sat Feb 25, 2006 1:20 am |
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| CCS ADDict wrote: |
so I need additional external circuit/IC to produce -5V...may I know how can I achieve that? |
If you have only a +5V supply, then yes - you need an additional something for -5V. If you don't need a lot of current, you can use a charge-pump inverter such as TC7660. It's simple, small and it requires only several additional 0.1uF capacitors to run. Of course it's not the only solution... Where do you get +5V from?
If you have an RS-232 transceiver in your system such as MAX232, you can get -10V from it. There will be a lot of ripple, but you cam mitigate this by adding large capacitors. This is a fairly non-orthodoxal approach. |
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CCS ADDiCT
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| Posted: Sat Feb 25, 2006 5:25 am |
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| I think...TC7660 is a nice 1 for me.. |
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bvq
Guest
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| Bipolar O/P |
| Posted: Sat Feb 25, 2006 12:06 pm |
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I would make a +/-5V bipolar supply using a simple DC-DC converter (or Maxim style charge pump IC). Then feed the I/O pin to a bipolar supply comparator with the threshold set to about 2.5V. When the O/P > 2.5V the comparator will O/P 5V and when the I/O is < 2.5V the comparator will O/P -5V.
You could make the comparator from a couple of transistors configured as a long tail pair. |
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CCS ADDiCT
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| Re: Bipolar O/P |
| Posted: Sun Feb 26, 2006 3:57 am |
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| bvq wrote: | I would make a +/-5V bipolar supply using a simple DC-DC converter (or Maxim style charge pump IC). Then feed the I/O pin to a bipolar supply comparator with the threshold set to about 2.5V. When the O/P > 2.5V the comparator will O/P 5V and when the I/O is < 2.5V the comparator will O/P -5V.
You could make the comparator from a couple of transistors configured as a long tail pair. |
sound like exactly what I did...dude...
have any schemactic sample or link..stuff?? |
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SherpaDoug
Joined: 07 Sep 2003
Posts: 1640
Location: Cape Cod Mass USA
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| Posted: Sun Feb 26, 2006 1:46 pm |
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If the +5V and -5V don't have to be very accurate you could use a MAX232 chip. To disable the voltage doubler just leave out C1 from pins 2 to 3 and connect pin 2 to VCC.
If you need accurate +/-5V you will need to get them from regulators and then they can be applied to pins 2 and 6 of a MAX232 if you leave out C1 and C2 (pins 4 and 5). Or you can use any other RS232 driver running from +/-5V.
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The search for better is endless. Instead simply find very good and get the job done. |
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