The datasheet says that the input is a differential amplifier. Therefore, one way of controlling the valve is to use two PWM pins, generate a 0 -> 10V signal from each one, and feed them to the inputs. Set one of the outputs to zero (depending on which way you want to move the valve) and the other to 0 to 10V. This requires 2 PWM pins to control the valve, but does not need a negative supply. The attached schematic is one way of generating one 0-10V signal.
Alternatively, only use a PWM pin to generate one of the inputs, and switch the other to 0V or +10V from a digital output pin.
If my german is good enough its a 0..10V control signal. But it is differential so you can connect either Ue or Ud to ground and get either sense as (Ud-Ue) is the control voltage (section 3.3.1.3 of the pdf) - anyone got a better grasp of technical german??
No but if you scroll down the data sheet the bottom half is repeated in English!
So yes it is a differential input. That means the two signals both go from 0 to 10V, it is just that when one is up and the other is down that is a 10V signal but when this is reversed it is a -10V input. But there is not a -10V with respect to ground it is just with respect to the other signal.
Therefore you need two 0 to 10V analogue signals. I would put the PWM first through a transistor to get it in the 0 to 10V range, and then filter it to remove the PWM switching noise. This is simpler than smoothing it and then having to get a linear amplifier to boost it up to 10V.
thanks for all the pointers and ideas- it seems that the catalog page was missing a bit of info that the data sheet filled in. who would have thought it
to move this thing in direction "A", apply a voltage to pin D, this voltage is ranging from 0-10v.
to move this thing in direction "B", apply 0-10v to pin E.
pin D and pin E are to remain connected to their respective branches of the circuit. i would imagine i could break something it 10v was on pin D and pin E at the same time?
the data sheet says that if only one signal pin is available, then the other needs to be grounded. since i will be using both signal pins - there is no need to ground the pin, when traveling in the opposite direction, correct?
i'll keep reading a bit and post a circuit sketch in a bit -- again thanks for the help
I agree with dc42 that his ckt should work, and all the way from 0V to 10V output, as the LM358
opAmp has input common-mode range down to ground.
The one thing that may be an issue is that 1st-order filtering of the PWM signal will leave a little
ripple on the DC-level, so the valve may jitter some. You can deal with that by using a PWM
frequency much much greater than the R*C time constant of his filter, but this will also reduce
the frequency response of the valve, if that's an issue.
thanks for the reply --- although it is bit above my knowledge level.
...filtering of the PWM
so if i look at it on a scope i'll see some stepped lines, and not super smooth, the faster the pwm frequency, the less noticeably this becomes?
...PWM frequency much much greater than the R*C time constant of his filter
??? the math of circuits has got me confused. i used to have respectable math skills, but haven't used them in many years. could you clarify a bit.
...response time of valve.
--slow is fine.
i'm putting together a parts order now... any suggestions?
For a 1st-order RC low-pass filter, the 3dB or 'cutoff' frequency is given by F3db = 1/(2piR*C). You want the
PWM frequency to be maybe 5X this value to get reasonably small ripple. Probably better to directly access
the Arduino PWM subsystem than to use the analogWrite() function, which I believe has a fairly low frequency.
BTW, I find I'm using google images for almost everything now, in preference to a regular google search. Easier
to zero in on the perfect website, :-).
That site is very useful. The result with those numbers is not very good, so needing something more like
Fpwm=10Khz, Fc=100Hz, or 100:1 to get low ripple.
5K and 10uF -> F3db = 3.18 Hz, which is quite low, but probably ok if all you're doing is changing slowly.
oric_dan(333):
That site is very useful. The result with those numbers is not very good, so needing something more like
Fpwm=10Khz, Fc=100Hz, or 100:1 to get low ripple.
5K and 10uF -> F3db = 3.18 Hz, which is quite low, but probably ok if all you're doing is changing slowly.
My suggestion was 100K and 1uF, giving F3db = 1.59Hz and time constant = 100ms. I guess we need to know how fast the OP needs to move the valve.
I'm confused at where the RC filter would be connected in the circuit. If I was switching a transistor with one of the pwm pins, the transistor is allowing the path to ground. Is the RC filter on the collector side or the emitter side? (thinking this is an NPN)
There is a path to ground via the capacitor, is the high freq. stuff is going this route? and that's the whole point...
No that is totally wrong.
Collector to pull up resistor to +12V.
Collector to filter resistor. Other end of resistor to capacitor to ground and also to one of the inputs of your controller.
You need two of these circuits one for each input. You also need a common ground.