About to pick up my MEP 003A

[edgephoto]

The panels do look interesting. I was thinking of taking a chance on one. Lucky I forgot the meters in the MEPs have separate transducers. The frequency meters from Simpson and Hoyt have direct connections to voltage rather than using a transducer. The load meters might actually work if you wanted to play around. In my mind it is not worth the effort.
The frequency meters and transducers seem to be troublesome, if you believe everything you read.

 

[Triple Jim]

That panel would cost me a bit over $80 delivered, but there sure is a lot of stuff on it for $80. The description says two meters are % rated current, not power, but it's hard to tell if that's correct. You can make a shunt to sense current, but I'm sure you know that if you're working with the Atmel. I wonder what the meter was that's been pilfered.

 

[leedawg]

Yup the one im still working on is sensing fq. Been thinking of using a step down transformer to drop the line voltage down to 5 v or so then use a diode chop the sine wave into a pulse train. Send that to an optocoupler and then feed that to the micro but have not had time to test it. Thanks for the suggestion on the shunt though for current. Thats how the analog DC high amp meters make their measurements as well.

 

[Triple Jim]

Maybe just use a couple resistors as a voltage divider and eliminate the transformer. Have the microcontroller sense the top of each cycle with something like a comparator IC against a Zener or whatever, and measure the time between each cycle.

Of course if your microcontroller has an A-D converter built in, you can find each cycle easily without the external parts.

 

[leedawg]

Not a bad idea I like it. Think some high resistance resistors would be safe enough being the only thing between the line voltage and the ADC pin on the micro? With the ADC yeah it would be easy just tell the software to count the peaks pretty much and then send out a PWM signal to the meter to drive the needle. Ive been playing with the Atmega 168 for this project and will probably move it to an ATiny once I get it actually working and the bugs ironed out. Time always seems to be the thing I run short on with work and all.

Thanks for the input again.

lee

 

[Triple Jim]

I wouldn't be worried about the resistors, just choose them properly so they don't get overly warm and maybe put a Zener at the input pin to get rid of any spikes that might sneak in. I'm most familiar with the Intel 8051 family and all the others that followed like the Signetics 87C552, etc. If your Atmel has a D-A converter, you can send out a real analog voltage to the meter, but the PWM fake-out is fine. I love stuff like that, it'll be a fun project.

 

[leedawg]

Nice yeah I dont know much about the intel series, ive only played with the atmel's and the pic. I too love micros they can do so many amazing things and are dirt cheap packed full of features that are endless as long as you have some imagination and ingenuity with the software. I like the idea of the zener diode to elminate the spikes. Thanks again for the suggestions will have to start work on this again maybe this weekend.

 

[Triple Jim]

Yeah, I'm old... I do all my programming in assembly, too. I find it soothing.

 

[storeman]

Ah, the language of the young. Perhaps, when you two arrive at a workable solution, might you post a do-it for dummies?

Jerry

 

[Triple Jim]

Jerry, I'm about to turn 55. Is that still young?

 

[leedawg]

**** Assembly boggles my relatively young mind (32). Thats what I like the atmel cause I can program them in C which I find a little easier to get my head around Yeah Ive been planning on posting a DIY in the future once I get it all to work and have the time to write it up. After it works it will be pretty easy to do I will just post up the software to make it work and you just buy the parts and solder it all together.

 

[LuckyDog]

While I love what these last set of posts have been talking about.....
[I too work with microcontrollers and just these types of circuits]

I think the thread is being hi-jacked. Please start a new thread with this topic. I can see it getting a lot of hits and input. There are super smart guys are here with experience dealing with Freq and Current measurements on the 002A and 003A. Plus, I'll bet the other older MEP gens could benefit.

 

[3rdaavbn]

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