Duel rail voltage

[Gregory]

I have 24V dc supply and i require +6v dc rail and -6v dc rail I .
The 24 volt supply is required for a nother function . I require the duel rail supply to opperate a Automatic watering systom using electrodes in the soil to switch on the systom I am using a IC LF353.
I require a circuit digram to obtain the duel rail voltige as I do not know how to split the voltage I can ruduce the voltage from 24 to 12 .

 

[Hero999]

What current do you require?

For low currents (<30mA) you can use zener diodes or an op-amp with zenners on the output.
For medium currents, (30mA to 2A), it's probably best to use an op-amp buffered with transistors and a linear regulator on the output.
Foreven higher power levels a switching requlator is the probably best solution.

What is the "other function" required from the 24V supply? Does it interface with the circuit requiring the +-6V supply?

Please post the circuit that requires a +-6V supply, you might be able to convert it to +12V single rail or even +24V single rail.

 

[Gregory]

Automatic Watering System

I have Made a printing error on the circuit digram. the rail voltage is +6 and -6 Not+5 and -5 Volts as showen.
The +6and -6 RAIL VOLTAGE supplies the relay and the auto watering circuit and require the split rail for the LF353 IC.
The watering circuit is opperated by the Electrodes into the soil where the moisture completes the Circuit and there is also manual timers thet work in conjunction with the electrodes so I can regulate the time period and the moisture content.
I will try to attach the circuit to this message. If i do not I wil have to get help on how to post the Circuit.

 

[audioguru]

The easiest way to get -6V is to use an ICL7660 voltage converter IC.

Your circuit won't detect moisture. It is rectifying the constant output from the opamp oscillator instead of the changing signal level from the electrode. Move the rectifier.

 

[Gregory]

The moisture at the electrodes stops the relay from being opperated which inturn prevents the water solenide from opperating.This is what I require for this project.( the manual timers will give me more flexibility with the opperation)
If the circuit dos not do what I require then could you modify the circuit with the -6and +6 voltage rail ( which is taken from the 24V DC supply )and post it for me.

 

[audioguru]

The moisture at the electrodes stops the relay from being opperated which inturn prevents the water solenide from opperating.This is what I require for this project.

The rectifier diode is in the wrong position for this to happen. Move the rectifier do that it connects directly to the electrode, not directly to the oscillator.

If the circuit dos not do what I require then could you modify the circuit with the -6and +6 voltage rail ( which is taken from the 24V DC supply )and post it for me.

The ICL7660 voltage converter IC is simple. It uses the +6V that comes from a voltage regulator or something plus two capacitors and makes -6V.

 

[Hero999]

You probably don't need +-6V, +-5V will do.

The transformer isn't a 1:1, it must be a 10:1 to get 24V from 240V.

That relay is rated at 12V so it probably won't activate unless it's powerd by more than about 9V, use a 6V relay.

I don't see any reason why you can't generate the +-V supply from the 24V supply on your transformer. The circuits attached will work, the first uses zenners and can supply about 30mA, so it might not work for your relay uses more than 8mA, the second uses regulator ICs. You could also use bufferd zenners, like the one in your 3V supply, but you'll need a PNP trnasistor for the negitivce supply.

 

[kchriste]

hero999,
You might want to rearrange the diodes or you'll let the smoke out.
It would be even better if he had a center tap on his transformer, but something like this will work ok:

 

[Gregory]

I have looked on the net and in data books for a data sheet on the IC L7660
with no luck can you tell me what sight I can obtain this information or can you provide the information for me.

 

[Hero999]

Corrected, sorry I should've read the whole thread first and even if I didn't I still should've noticed.

Note also that both C2 and the capacitor I added should both be rated to 35V.

 

[audioguru]

The voltage converter IC number is ICL7660, not L7660.
I get datasheets from www.datasheetarchive.com but there are many other sites.