Current draw meter and logging history of current usage

[Judo]

I've just purchased a 65L no-name 12v fridge from ebay. As much as I think my battery and solar setup will be able to handle it at least for a few days, whether it's 1-2 days, or 4-5 days, is largely unknown unless I can record some power usage stats on the fridge in different operating conditions.

I love nothing more than a good set of statistic to graph and analyse! So what device can I use (I assume it would go in-line in the fridge circuit) to record a history of current draw from the fridge over time? Something i can connect to a laptop on the road to save the data would be ideal.

Any suggestions on devices that can do this?

[Graeme]

I have a multi-meter with data logging capabilities to an RS232 i/f to connect to a laptop. IIRC it records at 1 second intervals. However max time for greater than 400mA is only 15 seconds so of no use in this application.

[scarry]

There is a company here called tech rentals that would more than likely have something that you could hire,probably not cheap though.

Dunno if they are in your area as well.

I would borrow,purchase,whatever a clamp meter that will check DC amperage and that should give you some figures to start with.I have one of these clamp meters but am a bit far away or i could check it for you.

[Judo]

Although not the out of the box solution I was hoping for, this is very temping.... I already own an Arduino that could read the sensor. Just need to think about how to store the data historically.

$2 Carabiner AC amp sensor (aka current transducer, CT sensor, amp meter, split core clamp-on ammeter) (http://www.instructables.com/id/2-Carabiner-split-core-AC-transducer/)

[scarry]

would it work for DC?

Maybe not

[Judo]

I have had limited experience with these sensors before, but yes I believe that style of sensor works for both AC and DC, however the calibration would be different. It's just a coil around the power feed. I can't see how it wouldn't work.

[clubagreenie]

In relation to the indestructable. I understand the concept of creating the ring to sense, but, he's got it plugged into a multieter that has a clamp. It's not clear if that's just for demo purposes or it works on something that the clamp wont (DC or AC).

[Judo]

I think he was just using the multimeter clamp to calibrate the homemade one. Then he connected the homemade ring to the multimeter in mV mode. I.E. Something else could read the mV reading.

[bee utey]

You can't use an inductive coil to measure DC current. You have to use one with a Hall Effect sensor that creates an output voltage proportional to the magnetic field. And the ones I've seen are difficult to use on low currents as the field strength varies within the sensor. I would use a current shunt myself or a multimeter suitable for the job.

Suitable meter?

UNI-T UT71B Intelligent Digital Multimeter 2 PC USB Data Logging | eBay (http://www.ebay.com.au/itm/UNI-T-UT71B-Intelligent-Digital-Multimeter-2-PC-USB-Data-Logging-/170941018167?pt=AU_B_I_Electrical_Test_Equipment&hash=item27cce0f037)

[mark_coffey]

check out plasmatronics line of solar charge regulators, they will give charge current, load current, saturation of charge, and cumulative charging and loads for 24hr periods. they will also give 30days of data. Have been using these units on industrial applications and have one on my camper, very good for all of the data. www.plasmatronics.com.au/ (http://www.plasmatronics.com.au/)

I have used the PL20 and the Dingo, I installed a PL20 in a mates camper, we found the solar charge capacity of the panel didnt match up with his daily load, installed a bigger panel, he has never flattened the batteries.

[Judo]

You can't use an inductive coil to measure DC current. You have to use one with a Hall Effect sensor that creates an output voltage proportional to the magnetic field. And the ones I've seen are difficult to use on low currents as the field strength varies within the sensor. I would use a current shunt myself or a multimeter suitable for the job.

Suitable meter?

UNI-T UT71B Intelligent Digital Multimeter 2 PC USB Data Logging | eBay (http://www.ebay.com.au/itm/UNI-T-UT71B-Intelligent-Digital-Multimeter-2-PC-USB-Data-Logging-/170941018167?pt=AU_B_I_Electrical_Test_Equipment&hash=item27cce0f037)

Interesting. Did some reading and looks like a hall effect sensor is very similar to an AC current transducer, but needs power to operate. But yes, the further reading did reveal the cheaper devices are AC only. :mad:


check out plasmatronics line of solar charge regulators, they will give charge current, load current, saturation of charge, and cumulative charging and loads for 24hr periods. they will also give 30days of data. Have been using these units on industrial applications and have one on my camper, very good for all of the data. www.plasmatronics.com.au/ (http://www.plasmatronics.com.au/)

I have used the PL20 and the Dingo, I installed a PL20 in a mates camper, we found the solar charge capacity of the panel didnt match up with his daily load, installed a bigger panel, he has never flattened the batteries.

It looks like a decent solar regulator with data logging capability is probably the best way to do what I want. Solar panel and load stats are just what I want. I guess I was hoping for a solution less than $300!! I already have a (cheap) 10A solar regulator. Seems like a high price to pay for a pretty graph. ;)

Cheers guys. I'll have a think about it!

[Radz]

A Dick Smith clamp meter Q1476 which has both D.C and A.C capability should do the trick.

Does not have logging capability but whilst about the campsite just take a few readings from time to time.

Apart from anything else a useful multimeter.

[jarrods]

I use cheap amp hour meter which is wired inline with the fridge or whatever load you want to measure. I have put Anderson plugs on each end so it it plugs straight in. It measures volts, amps, amp hours, watt hours and few other things I can't remember. If you are wanting to measure drain on a battery there is no better way tan to measure amp hours. I think this one was about $40.

53983

[Judo]

Digital DC Ammeter, Amp Hour Meter, Watt Hour Meter (http://www.rc-electronics-usa.com/ammeters/dc-amp-meter.html)

This is more my price range! Wire this into the fridge circuit could work....

P.S. Obviously can't log to a laptop, but maybe I'll give that up if the device keeps a grand total...

[jarrods]

Google Mandrakes solar power. He has them for $35.00. That's where I got mine he was the cheapest by far and he is based in Australia.

Jarrod

[OffTrack]

Came across this which seems like it might be a solution:

https://www.sparkfun.com/products/9028

edit: seems to be out of stock at present.

Edit edit: there are similar products from other vendors which seem to be designed for the RC mob to log lipo battery pack performance. The output levels are designed with microprocessor ADC use in mind so should be perfect for a pic or arudino.

Datasheet is here: AttoPilot Voltage and Current sensor (http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Sensors/Current/DC%20Voltage%20and%20Current%20Sense%20PCB%20with% 20Analog%20Output.pdf)

[Judo]

Google Mandrakes solar power. He has them for $35.00. That's where I got mine he was the cheapest by far and he is based in Australia.

Jarrod

Yeah that does look good. I found a very similar product on ebay as well.

eBay Australia: Buy new & used fashion, electronics & home d (http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=251190995437&fromMakeTrack=true&ssPageName=VIP:watchlink:top:en#ht_3151wt_908)

Almost the same price, so I'd probably purchase from the Aussie place.

One in the fridge circuit and one between the solar reg and battery.


Came across this which seems like it might be a solution:

https://www.sparkfun.com/products/9028

edit: seems to be out of stock at present.

Edit edit: there are similar products from other vendors which seem to be designed for the RC mob to log lipo battery pack performance. The output levels are designed with microprocessor ADC use in mind so should be perfect for a pic or arudino.

Datasheet is here: AttoPilot Voltage and Current sensor (http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Sensors/Current/DC%20Voltage%20and%20Current%20Sense%20PCB%20with% 20Analog%20Output.pdf)

I found it here as well.

AttoPilot Voltage and Current Sense Breakout SEN-09028 (http://littlebirdelectronics.com/products/attopilot-voltage-and-current-sense-breakout)

It does look perfect for use with an Arduino.



I think the answer to keeping a log history is one of those mini sensors and an Arduino. Being that I'm both impatient and don't have time to be programming my Arduino at the moment (it's been sitting on my desk for months now), I think the next best "out of the box solution" is to purchase a $35 "watt meter" that provides a cumulative power reading.