digital input to switch on and off analog output
I want to use a digital input to switch on and off a defined voltage at the
analog output. The voltage should only be on as long a high signal is at the
digital input. I need this relatively fast so I wonder if this could be con
trolled just by hardware.
Any help would be appreciated.
Leave a comment...
- 3 Comments
I?ve attached a screenshot of a program that does something very close to wh
at you?re asking. A pause trigger is used on one of the counter lines,
which clocks the analog output. The digital input is what triggers th
e pause. However, the
analog output will not return to a known voltage ? you would have to add thi
On the other hand, this program would be very easy to create if you could ju
st use software timing for the digital trigger. You could just read a
Boolean, and then use a case structure to switch the different analog output
Lastly, I would ultimately recommend using one of the USB relay modules.&nbs
p; These are designed specifically for tasks like the one you?ve described.
I hope this helps!
example.jpg:#1; Sun, 18 May 2008 19:50:00 GMT
If you really want it to work fast, you'd better try to use a MOSFET. Switch
it on and off using the signal you want to apply to the input. Keep th
e voltage on the Analog Output constant (the one that you defined). Plu
g the transistor into your
circuit, so that it would modulate the output voltage.
If you send me more details about what you want to get I might be
able to sketch a circuit for you. Typical response time
of a MOSFET (a cheap one) is better than 0.5 us (and dow
n to nanoseconds). &nb
Sergey.#2; Sun, 18 May 2008 19:51:00 GMT
I attached two easiest (up to me) variants to do that.
The only thing is that the transistor will be open only while TTL is high. I
f you can vary the length of the TTL pulse than it's fine.
Another question is whether you need all that. According to your description
(diode laser, CCD) you are doing some experiments in the lab. If so, y
ou must have a pulse generator (if you don't have it, ask next door. This ki
nd of stuff is available in
EVERY lab). Trigger this pulse generator with your TTL and it will give you
analog output pulse you desire.
If there is no pulse generator available, than try with FET.
In the scheme Rballast should be much greater than the input resitor of your
laser (if it's 1 MOhm, take 10 MOhm for Rballast).
Scheme.jpg:#3; Sun, 18 May 2008 19:52:00 GMT