calculating resistors needed for a 0-5V E/P controller
calculating resistors needed for a 0-5V E/P controller
(OP)
i have a circuit that i need to switch between a couple different voltages to give an E/P 0-5V controller. right now, i am planning on using a 5VDC supply wired to two different resistors and a 2 position switch (to select either resistor), in order to feed the E/P with two different voltages. is the E/P current draw the only number i need in order the calculate the resistor size needed to feed it 2 and 4V for each switch position? i also have a 0-5VDC transmitter that will be loop powered to a display unit, so do i need to add that current draw as well when calculating the resistor size needed?
thanks in advance.
thanks in advance.





RE: calculating resistors needed for a 0-5V E/P controller
TTFN
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RE: calculating resistors needed for a 0-5V E/P controller
RE: calculating resistors needed for a 0-5V E/P controller
BTW,the 4.75 kohms you mention is the input impedance. Not something you should have in your supply (or control) circuit.
Leave this to someone that knows how.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: calculating resistors needed for a 0-5V E/P controller
RE: calculating resistors needed for a 0-5V E/P controller
Moreover, that datasheet also indicates that it's supposed to be a in closed-loop system, so a fixed voltage will probably not work correctly, since there's nothing to correlate with the actual pressure produced.
TTFN
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RE: calculating resistors needed for a 0-5V E/P controller
Power and signals are very different. It gets extremely tricky to try and mix the two. Provide 5V to your micro and 24V to your sensor, and make sure you have a bypass capacitor at the sensor and your micro.
First, make sure you have a voltage output (OB1TFE) and not a current output (OB1TFI) unit.
All you need is a voltage divider to convert the 0-10V signal to a 0-5V signal, so something like 20K in series with 20K will work. If you don't know what I'm talking about then Google 'voltage divider'.
A capacitor in parallel with the lower resistor will help knock out noise. Just be careful you don't slow your response down too slow.
The 4.75K is actually the output impedance of the sensor, so that will add to the top resistor in the divider and actually give you a slightly lower output. If you aren't driving an A/D input you may need to tweak your values a bit to stay at the proper logic levels; watch out that the 4.75K may not be constant though.
John D
RE: calculating resistors needed for a 0-5V E/P controller
John D
RE: calculating resistors needed for a 0-5V E/P controller
the load resistance is 4.75k, and i want a 6V signal to the load, so from a 10V supply, i need a voltage drop of 4V across the 1st resistor, so a resistance ratio of 4:6 or (2:3) for the resistor and the load. this would need a 2.3k resistor in front of the load. (see attached for what i mean)
would that be right?
RE: calculating resistors needed for a 0-5V E/P controller
RE: calculating resistors needed for a 0-5V E/P controller
John D
RE: calculating resistors needed for a 0-5V E/P controller
thanks again.