I need some hints how to make an interface circuit that would combine two signals into one:
- one is a Digital output is used to current sink (manufacturer wording) a load that is from 5V to 24V with a max current of 250 mA. This give a square like signal. Maximum frequency is 5 MHz. I refer to this as the digital signal or pulsed signal.
- programmable analog output, from -10V to +10V, at 16 bit resolution. I need only the 0-10V part. I refer to this as the analog signal.
The output of the combined signal are used to control the power settings in a machine and if it is on or not. This is done with one input at the machine accepting 0-10V as a control signal. 0V is zero power and 10V 100% power. The digital on/off signal determines if the voltage level set by the analog output is turned on or off at the machine. At the moment we are using a frequency of approx. 5 kHz on the digital signal.
The interface circuit is not driving the machine.
I have present a 24 VDC supply and 5V DC (500 mA) to drive the interface circuit.
I have been looking at using a operational amplifier, like the AD712, and a switch, like the ADG202A, to switch the operational amplifier on and off, is this a good solution?
As mentioned the analog output can be negative, but the machine should only be controlled with between 0-10V. Would the best place be to set a diode before the operational amplifier, as this mean the amplifier only handles positive voltages, and the interface circuit protect the machine from programs errors that would put negative voltages on the analog output?
I am sorry for my bad english and punctuation!
The analog output can provide 5 mA (2K Ohm) according to the documentation. The control input at the machine does not specify anything else than "control signal 0-10V"
Yes, this is my project on RentACoder.