Switching from +ve to -ve (Rather than +ve to 0ve)

Guest
I am trying to build a system using a 555 timer and logical gates and I have
come against a problem. I need my circuit to be activated by one switch. I
need the connecting or breaking of this switch to cause a drop in voltage
from +ve to –ve.
I am powering my circuit using a 9V battery.
I know how to connect the switch to my battery to cause the voltage to vary
between +9V and 0V, or connected slightly differently between 0V and –9V.
I have been recking my brains and I can't find out how I can make the output
voltage go from +9V to –9V depending on the state of the switch. If possible
I would like this to happen with low or negligible current flowing as this
would drain the battery.
Can anyone point me in the right direction?
Cheers
Robert
 
fake@reply-address.com wrote:

I am trying to build a system using a 555 timer and logical gates and I have
come against a problem. I need my circuit to be activated by one switch. I
need the connecting or breaking of this switch to cause a drop in voltage
from +ve to –ve.
I am powering my circuit using a 9V battery.
I know how to connect the switch to my battery to cause the voltage to vary
between +9V and 0V, or connected slightly differently between 0V and –9V.
I have been recking my brains and I can't find out how I can make the output
voltage go from +9V to –9V depending on the state of the switch. If possible
I would like this to happen with low or negligible current flowing as this
would drain the battery.
Can anyone point me in the right direction?
Cheers
Robert
Click to expand...
How many poles can the switch have?
 
In article <c3nd8f$sbs$3@newsg1.svr.pol.co.uk>,
<fake@reply-address.com> wrote:
I am trying to build a system using a 555 timer and logical gates and I have
come against a problem. I need my circuit to be activated by one switch. I
need the connecting or breaking of this switch to cause a drop in voltage
from +ve to –ve.
I am powering my circuit using a 9V battery.
I know how to connect the switch to my battery to cause the voltage to vary
between +9V and 0V, or connected slightly differently between 0V and –9V.
I have been recking my brains and I can't find out how I can make the output
voltage go from +9V to –9V depending on the state of the switch. If possible
I would like this to happen with low or negligible current flowing as this
would drain the battery.
Can anyone point me in the right direction?
Click to expand...
How about:

Ascii art:


+9V --------O
\--------- Output
-9V --------O


OR

!
-----
+9V -------O O------------- Output
!
\
/
\
/
-9V
--
--
kensmith@rahul.net forging knowledge
 
On 22-Mar-2004, kensmith@violet.rahul.net (Ken Smith) wrote:
OR

!
-----
+9V -------O O------------- Output
!
\
/
\
/
-9V
--
Click to expand...
surly we're talking short curcit when the switch is down?

unless, what do u mean by:
!
\
/
\
/
\
/
-9V?
 
<fake@reply-address.com> wrote in message
news:c3q1jh$4fu$1@newsg4.svr.pol.co.uk...
unless, what do u mean by:
!
\
/
\
/
\
/
-9V?
Click to expand...

That's a resistor. The idea is that when the switch is open, the output is
connected to -9v through the resistor; when the switch is closed, it's
connected to +9v directly.

The resistor needs to be small enough that when the switch is open, having
the resistor in series with the -9v isn't a problem; but you didn't tell us
what this is connected to, so it's hard to know. And it needs to be large
enough that when the switch is open and there's 18v across it, not too much
current flows. Since you're powering this from 9v batteries, you probably
don't want to draw more than a couple mA, so an initial guess might be
somewhere between 10k and 100k ohms.
 
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