Author Topic: PWM mods - V average VS RMS voltage (Read 8062 times)

Breaktru · « **on:** October 23, 2012, 09:37:27 AM »

Breaktru · « **Reply #1 on:** October 23, 2012, 09:51:50 AM »

CraigHB · « **Reply #2 on:** October 23, 2012, 02:02:42 PM »

That's a really useful tool. I had heard the Chinese VV PWM devices were way off, but according to that instrument, they're really off.

The reviewers brought up the Chinese manufacturing culture that allows products that don't work as advertised, but he gives them way too much credit. It's not a matter of not realizing what people want or care about, it's a matter of flooding markets with products made as cheaply as possible. It's what they do and it's always a case of buyer beware for consumers.

One thing no one ever talks about that is just as important as the measurements they see is the accuracy of the test equipment. Everyone just assumes their meter has no error. That device is going to have some amount, even if negligible. What assurances are there that this meter has significantly less error than the devices it's testing.

Breaktru · « **Reply #3 on:** October 23, 2012, 03:55:45 PM »

The more I look at the ECD Meter, the more I believe that we can make something like this too Craig. Watcha think
We already have everything it does built into the mod. How about reading RMS voltage?
Would it be a matter of just adding a calculation. Something like this?
Full Rectified Wave: Vrms= Vpk/sqrt(2)
Sine Wave: Vrms= Vpk/sqrt(2) or is it Vrms = 0.707 x peak voltage
Half Rectified Wave: Vrms= Vpk/2

ECDmeter

http://www.youtube.com/watch?v=F-_Aludj7kU

CraigHB · « **Reply #4 on:** October 26, 2012, 10:26:00 PM »

Was out of town for a few days, just got back, but yes, we can build something that does the same thing with the sensing hardware we're already using in our buck and boost mods. RMS values for current, voltage, and power are proportional to duty cycle (linearly for power and to the square root for voltage and current). So, it's just a matter of measuring peak current, peak voltage, and duty cycle then doing the math in code. We already measure peak current, but for DC, it's just output current. The caveat for PWM being we have to time the samples appropriately. Peak voltage is input voltage or battery voltage which we already measure for battery capacity indication. Duty cycle is set by the controller so that's known as well. So, all that's left is the math which can be done quite simply in code, as you've already indicated.

beamrider · « **Reply #5 on:** October 27, 2012, 12:12:44 PM »

I'd like to see something like this with an OLED type screen, to give you more info all at the same time...

Breaktru · « **Reply #6 on:** October 27, 2012, 12:45:41 PM »

The ECDmeter is made by Stoney. This is what he had to say about his attempt to use it. I don't think I would have a problem using the oLed as I used it in my DNA MCU mod.

Quote from: 'Stoney'

i might be offering the oled one in a few months but it has a few hassles.

its not readable while vaping which i find very useful to not thrash attys and cartos.
it does not have anywhere near the low voltage range of the existing LED one .. it works down to 3.3 at least, not sure how much lower, mostly a non issue.
its not as robust, so its going to need a case which will add to cost. this is the major issue.
its more costly to make. not too bad though.
it has a really annoying rolling flicker on pwm mods, i will work on this area next.

next offering is to be a VW module, i might look into ecd2 after that.

just concentrating on a few other things first.