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46  Using Arduino / General Electronics / Re: Understanding ACS7xx Current Sensor on: February 20, 2013, 07:26:32 am
yes i agree those designs are poor, not sure if those tracks are man enough for their intended currents tough, it took me about 6 attempts to get to this this design, i did a few versions where i had ground fill didnt work well, either. not a good idea to place tracks under the ic either, you have to isolate the pins either side.

the current path pins are as close as possible to the connector as possible and i then fill that track with solder from the connector to the 2 pins both sides to be sure  
47  Using Arduino / General Electronics / Re: Understanding ACS7xx Current Sensor on: February 19, 2013, 08:31:36 am
ok im stumped there, will look up 4 wire Kelvin set-up, thanks lefty.

ok i understand now thanks for pointing that out lefty

on a more practacle note ran my acs 712 30amp version, loaded it up to 10amps  ran constant for 5 mins, then checked it for its temp,  there was absolutely no heat in the ic casing what so ever.

according to the chart id be getting 80 ish dec C, in the chart it mentions Die temperature whatever this is? maby it the core of the ic itself maby? really not sure, but i didnt notice any heat generated at all @ 10 Amps, be nice to know what this die temp is though, i often hear case temp or package temp, but never die temp.
48  Using Arduino / General Electronics / Re: Understanding ACS7xx Current Sensor on: February 19, 2013, 04:13:22 am
All I will point out is the size of the eval pcb heat sink vs what the commercial resellers typically design and sell. The datasheet mentions a typical internal resistance of 1.2 mOhm for the acs712 and a 5x over current survival.

The datasheet also mentions a atypical 2oz copper thickness for the pcb used on the eval board. The FAQ also shows die temperatures assuming optimal conditions (ie eval board) reaching 165 C at 20amps in hot ambient conditions. I expected my device to potentially get hot inside as it did not feature active convection and the enclosure is small.

So, by all means go and use this sensor but between the relatively high error and the heat issues, if was not suitable for me. For those measuring short impulse loads in particular, this chip family features very attractive attributes like small size and relatively low cost. I went for the LTSR series from LEM instead. It's leads are significantly beefier, you get a reference voltage for differential measurements, etc.

hi, was a little worried when you quoted the internal resistance ive looked at the data sheet many times and never came across this figure, ive been using the acs 712 30amp chip for some time and never noticed a heat issue, im using their suggested circuit.

those internal resistance in the chart marked  "Typical Leadframe Resistance at Various Ambient Temperatures"

Are defiantly wrong ive just gone through all my 20amp and 30amp chips and measured this resistance
results as follows, these were measured on the pins nothing attached to them on ip+ (pins 1 and 2) and ip- (pins 3 and 4).

acs 712 20a  total 6 ics,  all 0.3 ohms
acs 712 30a  total 13 ics  all 0.3 ohms

maby the figure they quote in their chart has a typo (mΩ) sould be just (Ω)

they do mention that the data was made using theAllegro ASEK712 demo board maby this resistance comes from extra circuitry there maby? but looking at it cant see any components that would suggest this

be really great if someone else could also confirm this resistance as well

49  Using Arduino / General Electronics / Re: Current measurement on positive or negative side? on: February 15, 2013, 04:07:40 pm
smiley-red Oops, I saw the hall effect verbiage and assumed it to be an inductive pickup.  I see that it is actually in series with the circuit, sorry about that.  I think I'd look for an inductive pickup sensor if it were me.
hay, dont be sorry just pointing it out
50  Using Arduino / General Electronics / Re: Current measurement on positive or negative side? on: February 15, 2013, 08:52:26 am
Since the sensor is not actually carrying any current, it's not going to have any affect on safety either way in my opinion.  It's a hall sensor, meaning it magnetically measures the current in the wire, so circuit isolation is very high.

Is this for some kind of RC car?

current does flow through the sensor, on pins 4 and 5 -  ip+ and ip-
51  Using Arduino / General Electronics / Re: Current measurement on positive or negative side? on: February 15, 2013, 07:51:36 am
130 amps 24v

what sort of motor is that? im guessing some sort of automotive starter or alternator maby?
52  Using Arduino / General Electronics / Re: Current measurement on positive or negative side? on: February 14, 2013, 10:02:05 am
bloody hell 130a dc be careful with that, i used to work on lifts with very big dc generators scary stuff.
53  Using Arduino / General Electronics / Re: Current measurement on positive or negative side? on: February 14, 2013, 06:22:41 am
no it measures ac or dc, im sure it would work both ways, test it both ways
54  Using Arduino / Displays / Re: Are lcd's displays effected by Direct Light (not sunlight) mine is on: February 13, 2013, 03:45:52 am
hi liudr, yes i understand that, there is a 680r current limiting resistor on the lcd itself
55  Using Arduino / Displays / Re: Are lcd's displays effected by Direct Light (not sunlight) mine is on: February 12, 2013, 06:05:19 pm
this is my lcd setup
56  Using Arduino / Displays / Re: Are lcd's displays effected by Direct Light (not sunlight) mine is on: February 12, 2013, 02:46:55 pm
hi liudr thanks for taking a look

its backlit blue, white characters

here is the display


http://www.ebay.co.uk/itm/160930204992?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
57  Using Arduino / Displays / Re: Are lcd's displays effected by Direct Light (not sunlight) mine is on: February 12, 2013, 09:07:49 am
hi john
its really strange, ive tryed blocking out different parts of the display does this same gets dim in direct light, as soon as you angle it out of the light characters go bright a fraction of a second later, like an auto contrast display i soppose, but its not an auto contrast display
 
but its defiantly sensitive to bright natural light, not sensitive to artificial light at all, its one of these ebay specials, had a really good look at the display cant see any sort of light sensor

been playing with it for ages now its defiantly trying to auto contrast, in some way.

(ive got another display an auto contrast, it has a small sensor in the black front face, nothing like this one)

http://www.ebay.co.uk/itm/160930204992?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
58  Using Arduino / Displays / Are lcd's displays effected by Direct Light (not sunlight) mine is on: February 12, 2013, 08:26:34 am
hi,

got a really strange lcd problem, im using a bog standard 4 line 20 character display no problems at all been working fine for a couple of months now

i noticed a few times early on the display acting strangely the characters went really dim couldnt work out what was causing it.

fast faward 2 months finally worked out what is causing it, had the display close to a window the display went really dim all characters,  then took it away from the strong light not sun light into a normal lit room the characters returned to normal operation

is this normal?   
59  Using Arduino / General Electronics / Re: Chinese Pcb Manufacturer Reccomendation. on: February 12, 2013, 04:16:41 am
After seeing this I thought I'd email Sitopway for a quote.

Just received it and they quoted me 50USD for 10pcs 100mm x 100mm dual layer, red soldermask, top/bottom silkscreen on 16mm FR4.

That's 20USD more than Elecrow, so looks like I'll be sticking with them.

The OP said 5.2GBP for 130mm x 140mm, so I wonder if that was just per single PCB, ie 10 pcs was 52GBP? That would make more sense at about 80-90USD for 10 pcs 130mm x 140mm, based on what they have quoted me.


the board was double sided, 5.2 each including postage 7 day turnaround, for a 130mm by 140mm board, 81usd total
60  Using Arduino / General Electronics / Re: Understanding ACS7xx Current Sensor on: February 10, 2013, 03:37:45 pm
yes the output is very stable im measuring ac current, pvm out of a frequency inverter, my output is really stable nice sign wave no noise.

im using the suggested circuit in the data sheet, 1nf across pin 5 and 6
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