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And no, I can't really show the schematics or anything, but It's no big secret ...
If you were to trace out the components in the picture I showed above ...
You would find the EXACT schematic shown in the datasheet under the heading "Single Supply RMS Current Measurement". The only difference is that I used a different current transformer, and changed the "burden" resistor to 51 ohms. Otherwise, identical.
Add a little gain for the PIC's A/D and you're good to go.
hth,
DT
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Did I miss something?
Originally Posted by Darrel Taylor
Did I miss something or are you using the ACS712 in this circuit or not at all? It sounded like you were running this 712 into this but reviewing this schematic I don't think you are even using the 712 now.
David
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It does not use an ACS712 in that circuit.
I'm showing the LTC1966 RMS convertor, which is needed whether the signal comes from a current transformer, a hall-effect sensor, or just a BIG honken shunt resistor that would heat your toaster oven.
It's the RMS conversion that matters.
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DT
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understood.
I am sorry I am not trying to tick you off or anything but I have to question this one last time. What is pumping the same signal through the LTC1966 going to give me that I can't figure out myself? I guess that is the part I am having trouble comprehending. The ACS712 data sheet says it's good for sensing current for motor control, load detection, etc... No matter what the ACS712 is going to output a voltage that is in direct proportion to the current it senses. Granted it's going to follow the wave form of the AC current it's still going to be proportinate to the peak current arghhhhh I need to go do something else for a while and stop thinking about this.
I'm not giving up on this I know I will get it.
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I must sound terrible in my replies.
Everyone thinks I'm getting ticked off.
Tuff!
But when I see someone going down the same bad path I took, I'll just keep tugging on your belt trying to pull you back, saying ... Duuude, there's a cliff up there. Don't go that way.
Let's see here ...It IS!The ACS712 data sheet says it's good for sensing current for motor control, load detection, etc...
As long as you know how to compensate for the type of load you are measuring.
Not at all.No matter what the ACS712 is going to output a voltage that is in direct proportion to the current it senses. Granted it's going to follow the wave form of the AC current it's still going to be proportinate to the peak current arghhhhh
With RMS the peak doesn't matter anymore. The entire waveform is averaged over time, to represent the amount of current that flowed during a specified time period.
Small motors will generate fairly high peaks, but since there's not much load it can overcome each magnetic pole fairly quickly. So a short duration current flow over the course of 1 AC cycle will average out to maybe one fifth of what you would read from a "Peak value".
I hope not. You've already ordered the parts.I'm not giving up on this I know I will get it.
When you get down to doing the math. Come back and describe the parameters. I got that part down.
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DT
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Op Amp
No your posts don't sound horrible I'm just anticipating or hearing you in my head "What don't you get you idiot!" I'm just struggling with this my knowledge about electronics is below novice. I'm having trouble though locating the op am you mentioned TLV324 it looks like that comes up as a switch of some sort not an op amp.
Thanks
David
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Oops, that would be a TLV274.
I knew I should have checked that.
TLV274 is a rail-rail version of the LM324.
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DT
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