# plc control

hello all, i know it's not the right ng to post this question, but it's the
only good engineering ng on my server !
my question is:
i'm using a controller, the satchwell IAC 600, it has got 4 analog outputs
(0-10 V).
i need to connect 1 of these outputs to 8 modulating valves (0-10 V) . the
valves are to be connected in parallel.
is there any relay circuitry which i can use to interface the single analog
signal to the 8 modulating valves?
thanks.
--
Hasta Luego
(Faster than Bruce Lee)
snipped-for-privacy@INVALIDsofthome.net
If you're using an analog voltage signal the valve should have a very high impedance and require little or no current. The 0-10 V doesn't actually drive the valve: it has it's own power supply. You should be able to connect the valves in parallel without any interface devices.
Don
To add a little to what DCheck the impedance that each valve presents, and the minimum impedance that your output can drive. Determine the impedance of eight valves in parallel (1/r_net = 1/r1 + 1/r2 +...). If it is a higher value, you are home free.
If it is lower, you can make a little opamp (operational amplifier) circuit to put out a voltage proportional to its input, and as much current as you require. If you have Radio Shacks where you are, they sell components to do this as well as instruction booklets. A single opamp will invert the signal, so either you'll have to use two opamps in series, or "reverse the leads" on the valves.
David A. Smith
thank you very much that was helpful.
-- Hasta Luego
"N:dlzc D:aol T:com (dlzc)" wrote in message news:fOaTb.16076\$tP1.8030@fed1read07...
First, analyse the load, and review the available drive.
How much current at 10 volts (max) does each valve need? 1 amp 1 milliamp 10 milliamp??
How much current can the AO output provide? 1 milliamp 10 milliamp?
You will then immmediately realise that if each valve takes less than 1/8th the available drive current at max voltage, then you can directly wire the whole shebang togather: output to all valves.
If the total valve requirement is more than the AO can provide on its own, then you need a buffer amplifier. This is not rocket science, even so. Tell us more details then
Brian W
///
Here's a little more on David's op amp idea.
Take any op amp that can handle unity gain. Put the voltage input into the op amps + input connect the op amps output back to its - input
That's it! The op amp needs a power source capable of handling the drive current of course, at say 15 or 20 volts for a little headroom. Choose an op amp that can go all the way to the low rail without latching up.....
Brian W
thx again bryan, i was just planning the small network, i don't really deal with the electronics part, i mean the electrical contractor would do that.
anyway, each valve consumes 3 watts, and i think that it has got an external power supply (24 V-ac). as for the plc, i don't know the max amperage rating !
thx again.. -- Hasta Luego

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