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Old Mar 13, 2012, 05:23 PM
Micro Jet Pilot
Chris T's Avatar
Joined Jul 2005
2,091 Posts
Hi dev,
I am having a hard time getting what you mean. Switching the gate lines to input on the controller side will make the lines float and most likely the bridges will smoke when the lines are floating somewhere in the middle of the supply voltage. This doesn't switch the motor terminals to high impedance. You need 4 lines (maybe the sensing can be done with three) for a standard h-bridge. The A3903 should do with 2 wire control, cause it goes to high impedance when the 2 gate lines are 0. Hope I am reading this right. If so, the new board is going to be really freaking tiny

Chris
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Old Mar 14, 2012, 09:25 AM
Micro Jet Pilot
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Joined Jul 2005
2,091 Posts
I just ordered parts at digikey for more than 200Euro I should be supplied for a while. 3 mm x 3 mm receiver is on the way. 2 mm x 1.6 mm oscillator is out of stock but also ordered. Must be a new part, the only one I found that small. I can't wait!
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Old Mar 14, 2012, 11:43 AM
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What is this receiver going to run on? Is it 2.4 ghz or something else?
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Old Mar 14, 2012, 12:00 PM
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United Kingdom, England, Surrey
Joined Aug 2002
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Quote:
Originally Posted by Chris T View Post
Hi dev,
I am having a hard time getting what you mean. Switching the gate lines to input on the controller side will make the lines float and most likely the bridges will smoke when the lines are floating somewhere in the middle of the supply voltage. This doesn't switch the motor terminals to high impedance. You need 4 lines (maybe the sensing can be done with three) for a standard h-bridge. The A3903 should do with 2 wire control, cause it goes to high impedance when the 2 gate lines are 0. Hope I am reading this right. If so, the new board is going to be really freaking tiny

Chris
I was thinking that with the gate lines set as input they would be unable to source or sink sufficient current to switch on the mosfets, much like the condition the system is in as the ucontroller boots. Just to be clear I mean driving the gates of both the p and n in each half bridge from the same line, i.e. line per half bridge. Two other lines (set as input) would be required to sense the back emf.
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Old Mar 14, 2012, 03:28 PM
Micro Jet Pilot
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Joined Jul 2005
2,091 Posts
Dev, as soon as p and n FET are driven by one gate line, there is no high impedance mode. Thus, there is no reason for a sense line cause you can't sense. You need 4 gate lines for all 4 transistors, then switch off all 4 transistors by driving p mos gates to VDD and n mos gates to GND. These lines always need to be driven and you need to make sure the two transistors of one bridge are never switched on at the same time. Sensing is done on the motor terminals with two extra wires which are connected to the comparator of the controller.

Chris
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Old Mar 15, 2012, 01:54 PM
Micro Jet Pilot
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Joined Jul 2005
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derk, the receiver is a 434MHz FSK PPM kind of thing

The SI4311 is a new easy radio product from SI who took over IA whose chips were on the plantraco devices. The SI4311 is a 3 x 3 mm chip and I found an oscillator 2 x 1.6 mm in size. These two together plus one 0402 cap should make a very small narrow band ISM receiver with FSK modulation. I am sending PPM right from the trainer port.

Chris
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Old Mar 17, 2012, 08:48 PM
Micro Jet Pilot
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Joined Jul 2005
2,091 Posts
Sneak Preview

Hi,
here is how it's going to look like. A 10mAh lipo and 10mm fan. The new electronics is coming along well. The servo prototype is running already with the atmel driving the coil from 2 x 5 pins in parallel. I also wrote a calibration routine where you can center the flap with the fingers to program the 0 position. The result is stored in the eeprom so it is availlable after power down.

Chris

P.S.: The big thing is the tx module
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Old Mar 18, 2012, 11:16 AM
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How many amps do you think you will be pulling?
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Old Mar 18, 2012, 04:14 PM
Team30 Micro EDF
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Adelaide, Australia
Joined Apr 2004
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Yowsers!!!
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Old Mar 19, 2012, 12:49 PM
Micro Jet Pilot
Chris T's Avatar
Joined Jul 2005
2,091 Posts
Quote:
Originally Posted by boredom.is.me View Post
How many amps do you think you will be pulling?
Good question! I was aiming for 150mA motor current. The current required for the rx, osc, 2 hall sensors and 3 atmels not considering the servo currents, which are also driven by the atmels is close to 50mA. Servo currents are dependent on the load on the flaps. Don't know yet how much it is going to be, but not critical I think. Reducing the supply current of the atmels by clocking slower might help It should be fine with a 10mAh 20C cell though. If I need more motor power to lift the model, I will use a bigger battery and the relation of the currents will also improve I'll make it fly...

Chris

P.S.: I do have a cool idea for a tx
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Last edited by Chris T; Mar 20, 2012 at 12:56 PM.
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Old Mar 23, 2012, 12:10 PM
Micro Jet Pilot
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Joined Jul 2005
2,091 Posts
Yes radio link established. It's the most difficult part to setup a new radio tx rx pair. I never know if there is a radio signal, so I don't know if the tx or the rx has a problem if it doesn't work. This time both had trouble Now comes the optimization...


Chris
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Old Mar 24, 2012, 06:39 PM
TheyreComingToTakeMeAway!
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USA, ID, Coeur D'Alene
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Chris, you are the most dedicated hobbyist on rcg, i dont know of a single other member who builds every part and component himself, including the radio system!
i hope to see this one flying soon, as i'm sure you can do it!
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Old Apr 11, 2012, 10:24 AM
Micro Jet Pilot
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Joined Jul 2005
2,091 Posts
Hi guys, i am on holiday right now, so i can't post a photo of my new tx yet. There is one chip missing on the tx module on the previous image, which is the adxl330. It is mounted meanwhile and is doing its job great! Any idea how i am going to control my planes in the future?

Chris
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Old Apr 11, 2012, 10:46 AM
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Nintendo Wii handset?

This is really cool work Chris.
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Old Apr 11, 2012, 12:59 PM
Like a Boss
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Canada, BC, Whistler
Joined Jun 2006
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Wow Chris, just noticed your thread, great stuff man, i thought my 12mm fan was small good luck, will be following with great interest.
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