| Author |
Message |
Admin (Admin)
Board Administrator
Username: Admin
Post Number: 223
Registered: 10-2004
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| Posted on Sunday, June 25, 2006 - 7:36 pm: |
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Dave,
Try all switches off see http://www.technobots.co.uk/Technical/Electrical/Speed_Controllers/MD22%20V9.htm for full details.
You can see the version number in register 7 but for that you need to access the controller via the I2C interface.
Try the switches all off and let me know how it goes. If you are waiting for FS1's then they are due in on Tuesday but you can of course cancel them if you find you don't need them now.
Paul |
Dave Lang (Kronic)
Member
Username: Kronic
Post Number: 5
Registered: 6-2006
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| Posted on Monday, June 26, 2006 - 1:42 pm: |
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Will have a check on Tuesday night and let you know how it goes.
Cheers,
Dave |
Dave Lang (Kronic)
Member
Username: Kronic
Post Number: 6
Registered: 6-2006
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| Posted on Tuesday, June 27, 2006 - 10:43 pm: |
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Result. Setting to all off gets the controller working. Excellent.
One small problem is that if I go from stop to full speed quickly then the motors jump at about 8-10 Hz in small jerky jumps. Could this be because I have not put caps across the motors or could it be a different problem? The voltage rail does not dip considerably and the 5V logic rail is OK too.
Cheers,
Dave |
Admin (Admin)
Board Administrator
Username: Admin
Post Number: 225
Registered: 10-2004
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| Posted on Wednesday, June 28, 2006 - 7:01 am: |
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Dave,
I'm pleased to hear all it is working. Try some 10nF caps (ideally 1000V) across the motor terminals to see if that improves things or not. Suppression is normally required in most applications.
Paul |
Dave Lang (Kronic)
Member
Username: Kronic
Post Number: 7
Registered: 6-2006
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| Posted on Friday, June 30, 2006 - 8:22 am: |
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Morning,
I've found the source of the jumpy motors. It's the BEC. I have a little circuit that produces 5V from our 24V batteries but it must be faulty. Do you sell / know of any decent BEC circuits which I can either buy or make?
Cheers,
Dave |
Dave Lang (Kronic)
Member
Username: Kronic
Post Number: 8
Registered: 6-2006
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| Posted on Friday, June 30, 2006 - 8:34 am: |
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PS: My BEC powers the RC receiver and the MD22 at the same time.
The 5V output plugs into the RC power input and the servo line outputs provide the 5V to the MD22 control circuitry. Would you recommend me taking a separate 5V line to the MD22 from the output of the BEC instead of going via the receiver first?
The BEC I have made has 47uF and 100n caps across the input and output lines of the BEC and uses a basic 5V regulator chip (3-wires). Maybe it's the current? I know that when the motor jitters the 5V line doesn't change, and the ripple on the output is only 15mV max. I don't have an oscilloscope to check for spikes and interference.
If I plug a proper battery into the receiver (instead of using the BEC 5V output) and take the power via the servo lines still, then it works fine.
Any suggestions?
Cheers,
Dave |
Admin (Admin)
Board Administrator
Username: Admin
Post Number: 228
Registered: 10-2004
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| Posted on Friday, June 30, 2006 - 10:07 pm: |
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Dave,
We used to have a 4.5V regulator but was discontinued by the manufacturer. We do have a 3A variable regulator (1062-004 will work at 24V but at reduced current) in the battery products section which will work fine even though it is only a series shunt regulator. The logic 0V is internally connected to the motor power 0V so no problem there. The logic only draws some 50mA which can be easily sourced from the receiver without significant voltage drop but it is still better to go direct. I assume you are using a LM7805 or similar so your component values should be okay.
I would suggest though that you consider current loops in the ground lines. Not having tried it but I would suggest trying it without having the logic ground connected to ensure no loops exist.
Let me know what happens and do experiment as this can be a bit of a black art.
Paul |
Dave Lang (Kronic)
Member
Username: Kronic
Post Number: 9
Registered: 6-2006
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| Posted on Monday, July 3, 2006 - 9:34 am: |
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Hi Paul,
I tried removing the current loops by removing the 5V and 0V lines from the receiver to the speed controller and providing the controller with a separate 5V supply. The problem definately lies in the supply of 5V from the PSU board to the controller and not from the receiver to the controller.
I also tried adding more filtering on the PSU with no avail. I've decided to use a receiver battery to get around the problem in the short term. Will look into a different power supply in the future.
Thanks for all the help in getting my problem sorted out.
Cheers,
Dave Lang |
Admin (Admin)
Board Administrator
Username: Admin
Post Number: 230
Registered: 10-2004
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| Posted on Tuesday, July 4, 2006 - 9:15 pm: |
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Dave,
Just try removing the 0V connection from the logic ground. Putting a scope on it would help diagnosing the problem. If you are happy running off a 4.8V battery pack (which is my preference) then that's the way to go.
Good luck
Paul |
Dave Lang (Kronic)
Member
Username: Kronic
Post Number: 10
Registered: 6-2006
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| Posted on Wednesday, July 5, 2006 - 12:55 pm: |
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I tried that and it ran worse than before 
I think we'll stick to the battery pack as that works fine.
Thanks for your help
Dave |
