| Author |
Message |
Christopher Barnes
Unregistered guest
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| Posted on Saturday, September 30, 2006 - 7:36 pm: |
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I am trying to use a Pololu Low-Voltage Dual Serial Motor Controller (LVDSMC) (cat no. 1503-002) in a small robot which already works well with a Plolou Micro Dual Serial Motor Controller (MDSMC).
As I understand it, other than the voltage and current ratings, these two parts should be identical in terms of the pin connections and the serial commands required. However, despite the MDSMC working OK (and still works OK if I swap it back into the circuit) I am yet to get any success from the LVDSMC - not even any LED activity.
Serial commands are from a PIC18LF2680 (also sent to a PC which logs the bytes and confirms the baud rate and command byte details).
Are there any differences that I've missed or known issues or is the LVDSMC just faulty? |
Admin (Admin)
Board Administrator
Username: Admin
Post Number: 274
Registered: 10-2004
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| Posted on Monday, October 2, 2006 - 9:27 pm: |
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Christopher,
As far as we know the LVDSMC is fully compatible with the MDSMC. Other than needing a slightly higher logic supply (3V) it does suggest you have a faulty controller. If you are happy that there is nothing wrong with your connections and supplies, send it back and we will get it checked out. |
Corrie
Unregistered guest
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| Posted on Monday, February 5, 2007 - 7:08 pm: |
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Hello,
I have just received a Pololu low voltage dual serial controller from yourselves and I appear to have a problem.
With no motors connected the on-boards LEDs act as expected with no problems - in any direction and speed.
If I try driving motors (tamia dual gearbox type) then the first channel will cut out at anything over the smallest crawl speed (ie 5 will run, 10 will cut)- the LED cuts out for that channel and will not come on again until I power cycle the controller. The other channel works fine at any speed or direction. I've tried swapping the motors around in case it was stalling but with the same effect. Seems like the over-current detection (is there any) is kicking in way to early or its just plain broke ;-)
I'm using 5.5v for the motor drive and nothing is getting hot ..
Any ideas?
Regards
Corrie |
Admin (Admin)
Board Administrator
Username: Admin
Post Number: 389
Registered: 10-2004
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| Posted on Tuesday, February 6, 2007 - 12:11 pm: |
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Corrie,
There is no over current sensing which is why motors should be selected with stall currents below 5A (or 10A if in parallel mode). Your motors are within this range so unless you shorted out one side, then the power stage of the controller should be fine.
When one channel cuts out, does the other carry on working okay? What happens to the LED's on the channel that stops working if you select between forwards and reverse? Have you connected the reset pin to your cpu and have you put suppression across the motors? Could you also advise the logic and power supply voltages at the time you get the lock-up.
These controllers are factory tested so the probability of a faulty unit is very low so we would prefer to explore all possibilities before the controller is returned to Technobots. |
Corrie Griffiths (Griffc)
Member
Username: Griffc
Post Number: 1
Registered: 2-2007
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| Posted on Tuesday, February 6, 2007 - 9:06 pm: |
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Its worth noting that its the same channel that cuts every time ..
>>When one channel cuts out, does the other carry on working okay?
Yes no problem - accepts new commands too.
>>What happens to the LED's on the channel that stops working if you select between forwards and reverse?
With no motor the LEDs behave as expected - once the channel has cut out the LED goes out as stays out. The other channels LEDs work as expected - even after the other channel has died.
>>Have you connected the reset pin
Pulled high permanetly for now.
>>suppression?
Yes
Logic is 5V and motor power is 5.5V
Regards
Corrie |
Corrie Griffiths (Griffc)
Member
Username: Griffc
Post Number: 2
Registered: 2-2007
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| Posted on Tuesday, February 6, 2007 - 9:35 pm: |
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Cracked it ... needed the 'double cap to motor can' method of suppression rather than the 'cap across the motor supply' method.
Strange how it only affect 1 channel tho (motor 1 on pins 6&7 for info)
Regards
Corrie |
Admin (Admin)
Board Administrator
Username: Admin
Post Number: 393
Registered: 10-2004
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| Posted on Tuesday, February 6, 2007 - 9:39 pm: |
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Corrie,
Thank you for posting on the forum, makes our life that much easier.
You appear to have as you suspected a faulty channel. If you can return it to us with a note of your invoice number, we will exchange it. You may well get to try the replacement before we have chance to test the returned controller so could you post here if the replacement works okay. This is very rare to have a Pololu controller returned so we will send it to the manufacturer in the States as I'm sure they will want to know the cause of failure.
Regards
Paul
** Admin Edit, your post above was received whilst we were placing this reply so of course there is no need to return your controller now!! ** |
Admin (Admin)
Board Administrator
Username: Admin
Post Number: 394
Registered: 10-2004
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| Posted on Tuesday, February 6, 2007 - 9:42 pm: |
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I was wondering if the motor interference was causing a CPU latch up hence the question about motor suppression. I would not normally recommend the cap to can method but you learn something new every day. Good to see you have it sorted and the Pololu reputation stands good. |
tom walker
Unregistered guest
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| Posted on Thursday, August 30, 2007 - 11:30 pm: |
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Re. Pololu 3A Motor Controller with Feedback - Part No: 1503-004
1) If I have 2 motors that each draw 3A, can i connect these in series to a single controller?
2) Should the motors have a peak of 3A and normaly run at about 1.5A?
3) If I have a PC interface card that has 2 analog outputs:
- 0 to 5V, output resistance 1K5
- PWM 0 to 100% open collector outputs max 100mA / 40V
Can I use either of these to control the motor contoller?
Rgds,
Tom |
Admin (Admin)
Board Administrator
Username: Admin
Post Number: 573
Registered: 10-2004
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| Posted on Monday, September 3, 2007 - 9:36 pm: |
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Tom,
1) We would not recommend connecting motors in series as it can cause problems if the motors have differing loads although it can work for certain applications. In answer to your question, yes you can connect 2 motors in series as long as the total current does not exceed 3A.
2) Not sure of your question here, just ensure the total load is <3A.
3) The analogue output should be fine although the impedance seems higher than I would have expected but should still be fine. Remember that 2.5V is neutral, increasing or decreasing voltage will gradually speed up the motor in opposite directions. The controller does not directly support PWM input although you could convert this to an analogue voltage yourself.
For further info on this controller, there is a data sheet link in the product description on the Technobots website. |
David Norton
Unregistered guest
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| Posted on Monday, September 24, 2007 - 1:41 pm: |
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Hi Paul,
Following our chat last Thursday I ordered the Pololu 3 Amp Motor controller with feedback and the Solarbotics GM14a motor. Arrived first thing Friday.. excellent. I just want to check with you that it is behaving as it should.
My set-up is rather messy. USB/RS232 converter, Null modem cable, RS232/TTL Converter, Servo Controller, the Pololu speed controller.
The set up works but is not quite as I hoped. The practical dead band is between 145 and 110ms. Either side of 128ms the motor 'sings' but does not move. The minimum speed I can drive it is about 15rmp. I had hoped to go slower. Is this a limitation of the design, or something else (like my 4 x AA battery power supply)? There are occasional stutters in steady running. Is this electrical noise? If so can I do anything about it?
Will I get more control switching to serial control? Am I right in thinking I need to connect the Tx Rx and a separate regulated 5v and ground to a power supply? Just checking that I have to provide both 6v for the motor and a 5v for the logic (and also 12v for the other boards). There is no 5v out from the RS232/TTL converter I have. I guess I could use the 5v and ground from the redundant servo controller. Is there a better way?
Is there any return (Rx) signals.. there are non mentioned. If not does it need to be connected?
I am planning C# programing control (with the help of a colleague). Would a similar ramp protocol (as described under the Basic Stamp section)work in serial mode? Immediatly sending full power clearly puts a strain on the motor (I have virtually no load on the system to damp the acceleration). Under that Basic Stamp section it also mentions other pin connections. I presume this is irrelevant when using Serial commands.
Thanks in advance for your help.
Regards,
David |
Admin (Admin)
Board Administrator
Username: Admin
Post Number: 586
Registered: 10-2004
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| Posted on Monday, September 24, 2007 - 7:08 pm: |
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David,
Before we get into too much detail, can you advise the two jumper positions.
What is the servo controller you referred to in your text? Is this simply a hardware converter to output the 1 to 2mS pulse every 20mS?
There is no need to switch to serial control as you should be able to achieve equal performance what ever input signal type you use.
Electrical noise from motors can be a problem, putting a 10nF cap across the motor terminals is typically all that is needed but good wiring layout can also help. Check out this document for more advice on EMI http://www.technobots.co.uk/Technical/Guidance/EMI%20and%20how%20to%20deal%20wit h%20it.pdf
You also make reference to Tx Rx etc., not sure I follow this bit of your explanation.
No return signals from the controller, if you decide to use the serial input, it is asynchronous.
Regards
Paul |
Mike Black
Unregistered guest
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| Posted on Thursday, November 22, 2007 - 1:24 pm: |
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Question about Pololu 30A Motor Driver (Based on VNH3SP30)
We have been previously using L6203 DMOS Full bridge drivers for our application and need something a bit meatier and was interested in the 30A Pololu motor driver.
What I needed to know was that with the L6203 we make use of a free running state when the Enable pin is low. On the datasheet for normal operation for the VNH3SP30 the truth table (Table 11) only lists operating modes for when both the enable pins are high.
My question is can we access a free running state with the Pololu driver if we tie the enable pins low during normal operation? If so what levels should INA and INB be at?
Best wishes
Mike Black
Camcon Technology |
Admin (Admin)
Board Administrator
Username: Admin
Post Number: 631
Registered: 10-2004
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| Posted on Thursday, November 22, 2007 - 10:00 pm: |
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Mike,
Your question is pushing the limits of our knowledge of this product. Page 7 states that a low on the PWM line will turn off both low side switches, this may allow free running. Page 15 also describes pin states to disconnect the load which sound like that should cause free running. Sorry we cannot be of more help than this. |
Stephen Winch
Unregistered guest
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| Posted on Tuesday, January 26, 2010 - 2:49 am: |
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Hi,
I was wondering if it is possible to get the full board layout of the:
Pololu 30A Motor Driver VNH3SP30
as I plan to mount it directly on to a PCB board.
I have the basic dimensions of the product page, but the location of the input and output holes would be good too.
Cheers
Stephen |
Admin (Admin)
Board Administrator
Username: Admin
Post Number: 1193
Registered: 10-2004
|
| Posted on Wednesday, February 3, 2010 - 6:40 pm: |
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Stephen, all of the information we have is shown on our website. You could try Pololu direct or simply purchase the board and take your own measurements. |
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