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31  Using Arduino / Microcontrollers / Re: ATMEGA328p Standalone 8MHz @ 2.5v on: December 24, 2012, 10:09:51 am
Hard part is having a reliable precision device to start with to calibrate thr rest, unless its a precision current source it won't be accurate, unless its a precision resistor it won't be accurate, might as well just buy a better multimeter lol
32  Using Arduino / General Electronics / Re: Relay driver on: December 24, 2012, 08:39:02 am
I do believe the uln2083 had 500ma per channel, but I believe a total of 2.5amps for the whole device
33  Using Arduino / General Electronics / Re: Relay driver on: December 24, 2012, 08:30:15 am
You will probably need to use discrete transistors/mosfets to get that kinda rating , especially if its more than 500ma each ch, but why so much?
34  Using Arduino / Microcontrollers / Re: good source for ribbon cables w/connectors? on: December 24, 2012, 08:22:08 am
I've bought connector ends before and all I found was like each wire individually crimp on ones that ended up being a pain to do and didn't work that well, that's why I think it'd be worth to just buy a whole cable
But where would I get those ur saying? I think I've seen them before, and actually reused one before too
35  Using Arduino / General Electronics / Re: Variable Voltage Regulator on: December 24, 2012, 08:17:45 am
There's. A formula and many calculators online too that will tell you the ripple and response time of any RC lowpass filter at a particular frequency, less ripple makes it less responsive and vice versa
36  Using Arduino / General Electronics / Re: sound like a burnt chip? on: December 24, 2012, 08:00:29 am
I think it was pretty light contact, some I wasn't sure because some flux residue seemed to be in the way, I used the solder blob method and wicked away the excess hopefully that was it, I have a spare but resoldering them isn't too fun
Ill test it after work today
37  Using Arduino / Microcontrollers / Re: ATMEGA328p Standalone 8MHz @ 2.5v on: December 24, 2012, 12:16:43 am
Its probably like my meter, the regular (non shunted) terminal has a max 200ma current measue ability and it works just like that
You could alternatively put a precision 1 or .1ohm resistor in series with the supply and measure the mv across it to get the current
38  Using Arduino / Microcontrollers / good source for ribbon cables w/connectors? on: December 23, 2012, 11:06:30 pm
Anyone know a good source for ribbon cable type connectors?
I'm looking for a 16 pin single row, as well as a few others that I can find on ebay, but id rather get something sooner than 4-5 weeks
39  Using Arduino / General Electronics / sound like a burnt chip? on: December 23, 2012, 09:47:56 pm
I hand soldered a 328tqfp and I'm afraid I have burnt it, I took a while to solder it, the first attempt with hot air it didn't line up so I jad to heat the whole chip to move it, it was working for a day and now only works when I apply pressure to the chip, I metered out all the pins and they all have continuity, it just gets me because it works for a while, I left and came back to do some more programming and now this, id just swap it out but I wonder if anything else could cause this? I have proper decoupling ( 0805 .1uf cap under the ic) as well as a 10uf electrolytic <1in away so I don't think its that
Unfortunetly the only output I can see without my oscope is the lcd, but if I press reset and wait a sec then press down on the ic its not one sec into the program
It won't program unless I press down either : /
40  Using Arduino / Programming Questions / Re: calculating error, quickest way on: December 23, 2012, 09:10:24 pm
To keep it simple for now what I'm gonna try and do is that for when the frequency is <2700 scroll by frequency since there will be no error, >2700 start scrolling by OCR1A then update the frequency so it appears the frequency is being scrolled thru yet its still accurate although jumping around
41  Using Arduino / General Electronics / Re: Variable Voltage Regulator on: December 23, 2012, 08:31:38 pm
You can use pwm , a npn transistor and a low pass filter to directly get0-10v
42  Using Arduino / Programming Questions / Re: calculating error, quickest way on: December 23, 2012, 02:31:02 pm
Now that is an interesting idea, also would allow me to get those higher frequencies with a litle more accuracy
43  Using Arduino / General Electronics / Re: Automatic Switching to Battery on Power Failure on: December 23, 2012, 02:28:23 pm
Oh wow missed that, thought it was 12v battery,
44  Using Arduino / General Electronics / Re: Automatic Switching to Battery on Power Failure on: December 23, 2012, 10:23:05 am
Charging sla's aren't that bad, they are pretty robust(I toture them often with electrically abusive experiments), probably the most effecient way would be a mosfet, a regular diode would only be worth it at low currents, a germanium diode is better but still has current limitations(as well as heat)
Basically for that size battery you will want to charge it @.3-1amp constant current untill it reaches close to 13.8, then you have it constant voltage @13.8
Easiest way is to use a lm317 although @1amp you will need a heatsink
45  Using Arduino / Programming Questions / Re: calculating error, quickest way on: December 23, 2012, 02:36:56 am
How much did that board cost? Lol I already spent 70$ on this, and I'm finally just in the final proggramming phase working on the gui,
but unless someone can figure out that formula perhaps after a certain frequency I will just have it directly change the OCR1A number and display the frequency
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