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46  Using Arduino / Microcontrollers / how can i upload sketches to a smd 328 on: February 21, 2013, 08:26:14 am
hi,
im thinking of using a surface mount 328 instead of the dip version 328 just wondering how i can upload sketches to them ?
thanks
47  Using Arduino / General Electronics / Re: op amp question on: February 20, 2013, 02:57:31 pm
LMC662 looks perfect for what im after thanks all very much for the help
48  Using Arduino / General Electronics / Re: op amp question on: February 20, 2013, 01:04:40 pm
yes my supply will be 12vdc, why wont it go to 0v lefty?  whats the lowest v it will output?
thanks
49  Using Arduino / General Electronics / op amp question on: February 20, 2013, 11:45:40 am
hi,
ive got a simple exercise im going to try, i need to control 2, 0  to 10v's using just 1 10k pot just wondering if my circuit will work i intend using a quad lm324, also i was just wondering if i could control all 4 op amps using just 1 10k pot? (bottom circuit same as top sorry)

thanks
50  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  
51  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.
52  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

53  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
54  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-
55  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?
56  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.
57  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
58  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
59  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
60  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
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