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Old Dec 05, 2012, 02:22 PM
Micro Jet Pilot
Chris T's Avatar
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The final rx + blc board will be 12 x 5 mm.

Chris
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Old Dec 05, 2012, 02:29 PM
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Impressive!!!
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Old Dec 06, 2012, 07:13 PM
Who dares, wins
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You crazy microdudes are epic!!!! So smallll!!
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Old Dec 11, 2012, 05:37 AM
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Oak Ridge, Tennessee
Joined Dec 2007
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Hi Chris-

I received the second controller today, and just finished some quick tests.

It seems much the same as the first, even a bit worse. The throttle range is even narrower on all three test below. About half what it was before (all three tx'es) and speed the same (rpm-wise) Removing the prop makes no difference again, switching coil wires, etc.

I'll try it some more soon as I can, using a different motor (smaller and more ohms?) and whatever else I can think of. I only had a hour or so to spend on it tonight. Since both controllers worked for you I'm thinking the problem is at my end.

The odd sound in the vid is one of our beagles having a dream.

testing new sensorless controller (1 min 4 sec)
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Old Dec 11, 2012, 01:15 PM
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mudville
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ChrisT,

Check out the new hbridges from TI...

DRV8837,,, like an a3903 but higher current..
DRV8830.. I2c hbridge, for those with no pwm output on the CPU..

SteveH
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Old Dec 11, 2012, 02:08 PM
Micro Jet Pilot
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Joined Jul 2005
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Dan,

strange but interesting, still looking at your video. I would recommend to try a lower ohmic coil with a clipped prop, maybe 15mm diameter. This will get us closer to a edf setup. And use your scope to monitor the ppm signal. I would have assumed the motor to kick in harder and run faster when throttling up. Maybe the controller is really set for faster motors. Don't fear the amp draw, fear the low rpm Maybe that brings us ahead. And check if the radio signal is dropping out by looking at the rpm. Right, it must be the difference in your setup. That doesn't mean you are doing a mistake, maybe the controller doesn't cover the operating points of your motors. Pretty sure it is not a hardware failure, since both boards were tested and worked for me.

Chris

P.S.: Interesting also that I hear everything but the motor. It must be really low kv. The thing I'd expect is that when kv is too low for the controller, there is a timer overflow within one half revolution and then timing calculation goes mad. I am using an 8 bit counter and have set the ck divider according to the high rpms I have. As I said before, I never tested prop setups, so this seems to be the must likely explanation. Get the kv up, the load down and see what happens just for reference, I had 20 turns around the D6 x 5 mm magnet.
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Old Dec 11, 2012, 02:41 PM
Micro Jet Pilot
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Wow, rdson at 5V is 1/4 of the A3903. This is one of the best finds next to the SI4355 for years. Thanks a lot Steve! Now I just have to find a suitable solution for the different pinout...

Chris

Quote:
Originally Posted by shoutchen View Post
ChrisT,


Check out the new hbridges from TI...

DRV8837,,, like an a3903 but higher current..
DRV8830.. I2c hbridge, for those with no pwm output on the CPU..

SteveH
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Old Dec 11, 2012, 04:54 PM
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United States, CO, Westminster
Joined Jul 2011
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I wish i knew what you guys are talking about because this sounds very interesting!
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Old Dec 12, 2012, 11:25 AM
Micro Jet Pilot
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Joined Jul 2005
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chester, Rdson is the resistance of the motor driver. The lower, the more power you can draw at the same operating temperature. Also at same power level, the efficiency of the controller is higher. 1/4 of Rdson makes a huge difference. The rating is 1.8A vs .5A.

Seems like I already designed the new device into my 5 x 12mm board without increase of size. Doesn't look so nice but is still single sided

Chris
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Old Dec 12, 2012, 06:17 PM
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ChrisT

Did you port the Si4355 code from the SiLabs EZRadio examples to the T44?

SteveH
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Old Dec 13, 2012, 03:07 AM
Micro Jet Pilot
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Steve, that's what I am currently working on. I am using the Wireless development suite and the IDE from SILABS to generate sample codes. Then I copy and paste the easy config array, the check sum and the number of config words to the atmel code. Well part of that I have done. The easy config array syntax is compatible with atmel assembler. I generate an eeprom file from the assembler code with just the array pasted into the code. The 202 bytes are beeing transferred to the rx already. Tonight I will send the checksum too to see if everything went right. I am going through the c code in the generated IDE examples to see which programming sequence is needed. After easy config, there are only a few steps to do, I think switching to rx mode and configuring the GPIOs. The C code example is a little difficult to follow, cause it is separated in several files. But I made it almost to the finish line

Chris
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Old Dec 15, 2012, 07:26 AM
Micro Jet Pilot
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Radio link with the new SI4355 established!!!!

Chris
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Old Dec 15, 2012, 10:30 AM
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Direct or packet mode?

BTW, what technique do you use to solder the 20 pin
3mm qfn to the pcb? I am just starting to build smd stuff
around that size and wondered what has been successful
for others..

SteveH
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Old Dec 15, 2012, 11:48 AM
Micro Jet Pilot
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Hey Steve,
I am using direct mode so far to transfer the ppm signal. It is a bit different as I was used to from the SI4320. Looking at the rx data, it seems to be quantized according to the datarate setting. I probably have to set the data rate higher or use the raw data. The raw data looks fine but is probably not filtered and thus more sensitive. Either way, from now on, optimization is quite straight forward, no blind flight anymore I will try some different settings now.

Soldering qfn and bga is not difficult with a hot air rework station. Using the thin boards you can even heat from the bottom. I did so with the ldo and the crystal. The "big" 3 x 3mm qfn chips I pick with a tweazer and put it in place while applying hot air from the top. Once it is sticking, I push it down more so all pins make contact and very often I have to shift it into place, cause I didn't hit the place exactly. Most important is that you don't fear doing it wrong. It is very forgiving and you can always take the part off again or push it sideways. If it is close to the correct position, it will slide on spot by itself. I pre-tin the board and then add sticky solder flux. Go for it

Chris
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Old Dec 15, 2012, 07:01 PM
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mudville
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ChrisT,

Will do. So about your bldc controller, is it sort of like a cpu based replacement for
chips like the a1442? Or something else...

SteveH
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