Anyone know about "function generators"?

[Ira]

While playing around with my water softener flow meter project, I started thinking about ways that I could simulate the flow meter for testing purposes (something better than a 5Vdc wall wart with an inline momentary pushbutton switch). The flow meter puts out a 5Vdc pulse (133 pulses/gallon). So I started reading up on function generators like the B&K Precision 4001A and 4003A that Fry's sells. The documentation for these things is really pretty bad, so I can't tell if this will do what I want or not.

Any of you electronics guys know if these function generators can "look like" something that generates 5Vdc pulses? If it can, how do you hook one of these things up to do it? Is it just a matter of connecting the positive and negative leads to where the flow meter was connected? The confusing thing to me is that it looks like it generates a +-10Vac pulse instead of a 0-nVdc pulse. But then it talks about a "DC offset control" that suggests it can simulate a Vdc pulse. That's where it completely loses me.

Thanks,
Ira

 

[az1324]

Massive overkill to simulate a pulse train. What are you connecting it to? You could use any simple microcontroller or even a parallel port with a script to toggle a pin on and off.

 

[roussell]

Yeah, a function generator will do that, but it's way overkill for what you need. You can build a simple pulser for about $5-10 with stuff from Radio Shack. Google 555 time projects. If you can't find anything that suits, post back and I'll throw a circuit together.

You could also go low tech with a small motor, spinning disk with a notch, and a switch. That would work fine if this is a one-time thing and you're not an electronics person. take a variable speed drill and clamp it to a piece of wood, stick an L-Shaped piece of metal in the chuck (bent nail) and position a small lever switch on the block so as the nail swings around it hits it. You could also substitute a magnet door switch and put a magnet on the end of the nail, or you could simply have the nail rub a piece of metal as it rotates... Like I said, all very low-tech, but if it's a one-time thing it will get the job done...

Terry

 

[BraveSirRobbin]

HERE is a schematic from my Car Monitor How-To that uses a 555 FYI.

 

[Ira]

Thanks for the suggestions, and building something would be a good learning experience. But I want to get more into electronics as it relates to HA and home security, so I would rather go down the function generator path. A couple of hundred dollars for test equipment isn't too hard for me to stomach (especially given how much I've already spent on HA stuff in the last year), if I can understand how to get a function generator to do what I want to do.

As described in the "water meter" thread, I'm tapping into my water softener flow meter to monitor water usage. The flow meter generates a 5Vdc pulse. It will feed into an optocoupler circuit (to protect the softener electronics), then into a binary flip-flop counter circuit (to reduce the pulses), then to the counter channel on a Brultech ECM-1240. I want to use the function generator to simulate the flow meter pulse output.

Thanks,
Ira

 

[az1324]

You might want to consider something like this http://usbee.com/sx.html as a better investment if you don't need analog signal generation.

 

[mdesmarais]

Simple answer- yes it will do what you want. You can even use the SYNC output directly. Do you already have a scope to measure the output?