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481  Using Arduino / Motors, Mechanics, and Power / Re: 24V BLDC Motor + Dual FETs + Arduino on: August 05, 2012, 11:29:22 pm
What value resistors are in series with the gates?
You have to also take into account the time it takes to charge and discharge the gate source capacitance
which will be indicated in the fets data specs.
482  Using Arduino / General Electronics / Re: Trouble with a boost converter on: August 04, 2012, 09:38:40 am
If all you need to do is turn the converter on and off, the connect the Arduino output to pin 3 which is the shutdown control.
Converter runs when this pin is grounded, stops when this pin is high.
Connect the switcher chip Vcc to a decent 5v supply.
483  Using Arduino / General Electronics / Re: Trouble with a boost converter on: August 03, 2012, 06:16:52 pm
Only boost or inverting converters initially draw large amounts of current to start.
Buck converters (reducing voltage) arnt as bad as the switch is in series with the load.
But , any switching converter will have trouble starting when fed from a current limited
source like an Arduino output pin.
484  Using Arduino / General Electronics / Re: Trouble with a boost converter on: August 02, 2012, 09:06:21 pm
Your circuit cant start.
If you look at the specs of the switcher chip you are using, the minimum peak switch current is 0.65 A , typically 0.9 A
which is well above what the Arduino can supply.
These types of switcher chips are designed to run from batteries which can provide the initial current to start the switcher.
Once its oscillating, the current drawn is then determined by the load.
You need to supply the switcher chip with a 5V source that has at least a 1 A current capacity to get the switcher chip started.
485  Using Arduino / Motors, Mechanics, and Power / Re: Having probles biasing FETs in an inverter circuit. on: July 26, 2012, 01:44:31 am
You need to think this whole project through more thoroughly.
Its important to know what the Inverter is going to power as feeding a square wave into a 50 HZ transformer
will not produce a very friendly waveform.
Typically, small Inverters for converting 12 V to 230 V dont work like what you are designing.
Usually, the 12 V is stepped up to 310 V using a push pull Inverter running at around 25 KHZ using a ferrite core
transformer, and then the output is rectified to produce 310 V DC , which is fed into a high voltage H bridge
designed to produce a MSW (modified square wave) output.
Even then, its important to know what the Inverter is going to power, as some devices dont like square wave power.

486  Using Arduino / Motors, Mechanics, and Power / Re: Having probles biasing FETs in an inverter circuit. on: July 26, 2012, 01:17:13 am
Really need more Information.
What is the Inverter powering.
What is the ultimate output voltage, and power capability.
487  Using Arduino / Motors, Mechanics, and Power / Re: Having probles biasing FETs in an inverter circuit. on: July 25, 2012, 05:44:03 pm
Yes, the hi side fets dont their sources grounded, so the gate voltage has to be higher than the supply voltage, by whatever is needed to ensure
that the fet saturates properly.
As well, you have to turn all the fets on and off quickly which means that the gate source capacitance has to be charged and discharged quickly
and as well you have to prevent shoot through all of which a h bridge driver does for you.
488  Using Arduino / Motors, Mechanics, and Power / Re: Having probles biasing FETs in an inverter circuit. on: July 25, 2012, 05:18:23 am
You arnt turning the hi side fets on properly.
You need at least 10 volts between the gate and source to turn the fets on, and that means that if you only have a 12 V supply
you need at least 22 volts to turn on the hi side fets.
Google H bridge driver to find a suitable driver chip for your circuit.

489  Using Arduino / Project Guidance / Re: PV cell energy monitoring on: July 24, 2012, 08:07:30 pm
Are you trying to measure the maximum power output of the cell , or are you just trying to measure the variation over time .
Solar Cells only deliver maximum power at one point on their V / I graph, and using a simple load like a resistor or current sink
will not give you the absolute maximum power output.
It will work if all you are looking for is relative changes over time.
To extract the maximum power from a Solar cell you need some kind of peak power point tracking.
This explains what the problem with Solar cells is and why peak power tracking is needed.
http://en.wikipedia.org/wiki/Maximum_power_point_tracking
490  Using Arduino / General Electronics / Re: Protected LIthium Ion Charging Circuit on: July 23, 2012, 10:51:52 pm
A bit more detail on how the individual cells are protected from over / under charging would help.
Charging Lipos in series needs cell balancing circuitry and its unclear from your description whether this exists
or not.
491  Using Arduino / General Electronics / Re: P-channel MOSFET won't turn off? on: July 21, 2012, 06:40:33 pm
If you are using a ATmega32 or similar Atmel chip, the high output voltage of an IO pin
is only guaranteed to be greater than 4.2 V with a 5 V supply.
You cant guarantee it will be exactly 5 V.
492  Using Arduino / General Electronics / Re: Trouble with a boost converter on: July 18, 2012, 05:41:32 pm
Boost converters need a substantial amount of current to start, as they have to charge the output capacitor
before the converter starts regulating.
You really need to run them off batteries or a supply that can deliver a few amps , or they wont start.
Whats the current capacity of your 5 V supply.
493  Using Arduino / Networking, Protocols, and Devices / Re: XBEE quits working after while on: July 16, 2012, 06:18:16 pm
The problem is the 115200 kbs speed rate.
If you read the specs on the Xbee series 1 , its only capable of a sustained thruput of 80 kbs.
http://www.digi.com/support/kbase/kbaseresultdetl?id=2213

You will be overrunning the Xbees transmit buffer.
You either need to drop the speed to 80 kbs or less, or implement flow control.
494  Using Arduino / General Electronics / Re: Can I use this solar powered battery charger to recharge my AA batteries? on: July 15, 2012, 12:35:38 am
How many AA batteries do you want to charge at once, and are the batteries NiMH types.
495  Using Arduino / General Electronics / Re: Can I use this solar powered battery charger to recharge my AA batteries? on: July 13, 2012, 03:18:47 am
The batteries wont get warm.
Although the Solar Panel is rated at 1.5 watts, the most it can deliver is 100 ma .
Into a AA battery, either nimh or nicad , thats only 140 milliwatts.
Maximum charge voltage for a AA nimh is 1.4 volts.
Its a very inefficient way to charge AA batteries.
Those types of chargers are intended to trickle charge car batteries, which essentially stops them going flat
if not used for a long time.

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