Show Posts
Pages: [1] 2
1  Community / Bar Sport / Re: Anyone had a chance to play with LPC810 DIP-8 yet? on: November 10, 2013, 04:54:45 pm
The user manual UM10601, Rev 1.3, 22 July 2013

Document information
 ARM Cortex M0+, LPC800, LPC800 UM, USART, I2C,
LPC811M001JDH16, LPC812M101JDH16, LPC812M101JD20,
LPC812M101JDH20, LPC810M021FN8
LPC800 user manual

18.1 How to read this chapter
The analog comparator is available on all LPC800 parts.

The errata you linked to is a month newer than the user manual I pulled the above excerpt from.  You would think, they would also put a new rev of the user manual out.  That is pretty significant.

Constantly switching between the datasheet, user manual, CMSIS-CORE standards, etc; great margin of error for one piece to not jive together or get left out.

2  Community / Bar Sport / Re: Anyone had a chance to play with LPC810 DIP-8 yet? on: November 10, 2013, 04:08:37 pm
Probably won't help you much but,

In my search to start learning about ARM, I went with NXP to learn.  Was going to get the LPC8xx as it was small and comes in DIP if needed.  It's only analog feature is a comparator, no ADC.  Although there is some talk around about using that as a crude ADC.  I also believe you will have to bitbang PWM on that chip (if needed).

I decided to start off with a M3 and got a LPCXpresso1347.  They (EA) make a LPCXpresso8xx board as well.  What sold me on the board was that you can detach the programmer/debug probe part of it and use it to program/debug standalone LPC ARM builds.  However, they (NXP) keep their protocol closed on the LPC-LINK.  I believe adafruit sells the xpresso boards as well, but I got mine from Digikey.

Not a bad little board to learn about ARM.

3  Using Arduino / Motors, Mechanics, and Power / Re: Stepper Motor not moving on: October 13, 2013, 07:54:06 am
On the A4988 there is an on board 100k pull down resistor that pulls the chip's !EN! line to ground.  So it is enabled by default.  Most, if not all of pololu's little stepper driver's either have onboard or onchip pulldowns to have the default state enabled.

Schematic at bottom of page

You can try pulling it down stronger if you think through capacitance on the breadboard or excessive radiation could be overpowering the 100k pulldown and driving it high.

As what MarkT said, he is correct.  That is how I ran my Due-A4988.  If you supply the A4988 logic supply with 5V, it will expect 5V logic signals on the STEP, DIR, etc. lines.

On my Due, I used this library (although I haven't messed with my Due in a long time)  Although that is not a solution, it should work with the library you are using.

The only problem that I have had with my A4988s was some invisible (to the naked eye at least) contaminates that were creating shorts on the board itself.  This was self inflicted and was a result of me using the wrong type of flux on the board.

This is a stab in the dark if correcting the logic power doesn't work.  Have you tried to adjust the current limit on the A4988?  You may want to adjust it to just under your motor's rating to make sure it's getting enough current.  That is a pretty hefty stepper motor.

4  Using Arduino / Motors, Mechanics, and Power / Re: Stepper Motor not moving on: October 12, 2013, 07:09:04 am
My eyes may be failing me, but are the header pins soldered to the A4988 or are the headers stuck in the breadboard and the A4988 just sitting on the top of it?

If the headers are soldered to the board, I would check those joints/connections to ensure they are good.

Another possibility is if you connected/disconnected things while the A4988 was powered, there is a slight possibility that could have damaged it.

Also, post your actual schematic, picture and problem on the pololu site if you haven't.  They are usually very good at supporting their products.  Matter of fact they helped me out last year with a A4988 problem I was having.


5  Using Arduino / Motors, Mechanics, and Power / Re: Stepper Motor not moving on: October 11, 2013, 11:05:29 pm
How are you driving the A4988's STEP pin?

Every pulse on this pin should step the motor one step.  If it is just driven from a constant (say 5V output) it will step 1 time and no more.

I did not look at your pic in detail, however, from the schematic you posted and the picture the obvious thing missing is a capacitor (unless it is off the page).  Although I doubt that is what is not making it work.  Here is what pololu has to say:

Warning: This carrier board uses low-ESR ceramic capacitors, which makes it susceptible to destructive LC voltage spikes, especially when using power leads longer than a few inches. Under the right conditions, these spikes can exceed the 35 V maximum voltage rating for the A4988 and permanently damage the board, even when the motor supply voltage is as low as 12 V. One way to protect the driver from such spikes is to put a large (at least 47 µF) electrolytic capacitor across motor power (VMOT) and ground somewhere close to the board.


edit: just read after the fact you were using the built in library.  I have used the accelstepper library before with my due with success.  never used the 'built in' one.
6  Using Arduino / Motors, Mechanics, and Power / Re: Electric clutch? on: August 31, 2013, 12:14:07 pm
Got it worked out.

-Canned the reel and some intermediate pulleys
-Changed to a smaller pulley on motor (used as drum instead of to drive a belt)
-Hooked power up to different winding on motor that allowed more torque
-Electromagnet holds blade in up position
-Blade heavy enough to overcome intrinsic motor/pulley friction to come down with a good thump

Thanks for all the suggestions.  With what I had available, I could not get anything built that was lightweight enough.  Turned out better in the long run; a simpler system.

Thanks again,


Oh, If I do win the electric clutch ebay thing and it ends up being the right shaft diameter for my rider; push button blade operation here I come...
7  Using Arduino / Motors, Mechanics, and Power / Re: Electric clutch? on: August 30, 2013, 03:04:42 pm

That is a pretty good idea.  Probably the simplest to fabricate of my current options.  I like simple.  An elcheapo or used throw out bearing and throw out arm may be a good coupling/decoupling device.

I actually just got back from walking up and down the isles of my town hardware store looking for misc pieces for the fabs.  Almost picked up a clutch for a weedeater, but I figured if I spun it fast enough for that to actuate I would probably launch the blade out the top of my contraption.  The blade only has to travel ~5-6 feet to the top.

Thanks for your time.

8  Using Arduino / Motors, Mechanics, and Power / Re: Electric clutch? on: August 29, 2013, 10:20:29 am
Just to give you an idea of what that thing is used for above:

My current rider, you have to pull a lever to engage the blades in the deck (basically applies tension to a 'V' belt that links the motor shaft pulley to the main deck pulley).  More classy/expensive riders do this at the flip of a switch through an electric clutch.  They are usually pretty costly.

9  Using Arduino / Motors, Mechanics, and Power / Re: Electric clutch? on: August 29, 2013, 10:07:14 am
It is a standard electronic clutch for a riding lawntractor.

Cross referencing this part number to the OEM part number, which gives the lawntractor model it goes to, which gives the manual.

Or short, most modern residential riders are 12VDC systems nowadays.  Pretty easy test to determine current it will draw.  (The total charging system is 16A on the tractor).

Also helps that before my current career I was a licensed Wheelhorse, Toro, Yanmar mechanic.

It may not be usable/desirable, but as I am a hoarder of things; if I do get the bid and it at least works upon arrival, it will give me a little confidence in ebay and be useful in a future contraption if not used now.


10  Using Arduino / Motors, Mechanics, and Power / Re: Electric clutch? on: August 29, 2013, 09:52:54 am
Although I have never had the courage to buy anything on ebay, I found a type of electronic clutch I have been looking at for a pretty low price.  I'll throw a couple of bids at it (I currently have it at $11.00).

I will still move ahead as per post above in the mean time.

11  Using Arduino / Motors, Mechanics, and Power / Re: Electric clutch? on: August 29, 2013, 08:02:00 am
I believe I will have to continue and design/develop something myself.

Prior to posting, I had not only searched many search providers but browsed, bugged all hardware, motor, electric shops I could find.  As possibilities are endless and many times hidden from plain sight, especially for specialty applications; something may still pop up.  So far, most are either small and puny or large and bulky.  Ones that seem just right are outlandishly priced (probably not so for their intended market/application).  I have forgot to check the local junk yards, may give that a go this weekend.

I am going to start prototyping the following three this weekend:
1. Combination of Robin's ideas
2. A ratchet mechanism (used in everything from clocks to trailer winches)
3. Change drive system to lawnmower starter with bendix that will actuate gear connected to drum.  Blade held up by electro magnet.

Still hoping a magic plug and play solution will present itself.

Thanks for the awesome help so far.

12  Using Arduino / Motors, Mechanics, and Power / Re: Electric clutch? on: August 28, 2013, 03:49:51 pm
That sounds like a good solution.

That is the basis for the inner workings of some fishing reels like the one I'm using, albeit a smaller version.  I like mixing mechanical contraptions I have to fabricate into my little projects.

I may build a prototype of what you describe.  I have been modding old transformers today to turn them into electromagnets for testing as a release mechanism.  Wouldn't be too hard to turn them into some solenoids that connect the 'pins' of the drive wheel to the drum pulling the line.

As of right now the blade falls very good under its own weight.  I just have to be careful that any contraptions are lightweight enough to not counter the mass of the blade.  Just so I would not have to add weight to the blade, then motor power would increase, etc....

Thanks for your idea.  I have the time, motivation and general know how but I fall short of intuitiveness from time to time.

13  Using Arduino / Motors, Mechanics, and Power / Electric clutch? on: August 27, 2013, 06:39:58 pm
I have a Halloween prop that I made and has served me faithfully for a few years.  It is currently controlled by a PIC18.  I am switching to AVR and upgrading my mechanics in preparation for the upcoming festivities at the end of Oct.  Here is a description of my current rig:

It is a full size automated guillotine.
1. The main motor operates a pulley via a 'V' belt to another pulley that is connected to a bait caster fishing reel.
2. When the motor runs, the pulleys turn the reel which is connected to a strong nylon cord that through a couple pulleys, lift the blade to the top.  The motor stops when the top is reached.  The action of the reel holds the blade up.
3. When it is time for the super cool head slicing action; another motor with a 'hammer' connected to it, spins and hits the cast button on the reel and the blade slides down.
4. The victims head plops down, exposing goo, cool sounds, strobe lights, etc.
5. Another motor repositions head, and everything resets.

Although my fishing reel solution was the only one I could come up with in my original short design time frame, and actually works well, I am unhappy with it.

I would prefer something like an electric PTO clutch or similar to the clutch on an air conditioning compressor.  I also thought about fabricating a type of cog and lever/ratchet; it would add an eccentric sound as the lever hit the cogs as the blade was raised.  Then using a servo to lift the lever when it was time to lower the blade (using the spindle from a lawnmower pull starter to allow the reverse free fall action).

The blade weighs ~4lbs and the main motor is out of a run of the mill 120VAC 20" box fan.

The actual question:
Does anyone have any ideas for a new lift/release mechanism?  I would appreciate it.  I have not come across anything that looks like a viable solution as of yet.

14  Community / Gigs and Collaborations / Re: Interest in 1284P boards? on: August 10, 2013, 01:55:52 pm
When I was looking for a more stable 1284P prototyping platform, there were only two that sparked my interest:

1. The Atmel MEGA-1284P Xplained
2. and your board.

Didn't go with the XPLD because of the fluff.

I really like your setup, but I use JTAG for debugging and programming.

There are a few more options out there but all in all, for the 1284, choices are pretty limited.

I ended up making my own (I was tired of wires and thru hole components going everywhere).  Have all the parts, the PCBs will arrive in 3 days.  Here is a rendered pic if curious. I don't have a cool name (or any) for it.

If you make a through hole version in the future with JTAG broken out, I will definitely be interested in purchasing one or two.  I like the idea of being able to swap out the chip if needed.

15  Topics / Device Hacking / Re: Hack garage door opener Liftmaster 973LM on: July 22, 2013, 08:34:04 pm
I would be happy to share all code, schematics, pcb layout and BOM.  However, I do not use the Arduino IDE or its libraries to program the AVRs. (I do use the Arduino libraries for my Due though).

My advice would be to continue to study/experiment with C/C++ and Arduino's twist on it. Have a plan for your code as well as your project and write your code in a way (ie document it well, use good structure/form, smart variable names, etc) that allows you to build upon it as you grow.  Verify/validate in small blocks.  When you hit a bump or what you might think is an obstacle, use it as a chance to rethink, research and retry.  Then come here to the forum; share what you're trying to do, what you've tried and what's not working.  Better to learn the how than the what.

I did the same thing as it seems you are doing.  Prototyping on a larger frame (my case an ATmega1284P), see what your code size is when your done, then pick the appropriate chip or Arduino to use for the finished project.  Then you still have your most likely more expensive prototyping board to start the next project.

I am in no way an expert or even know half of what I'm doing but if you need anything I may have for this project let me know.

Pages: [1] 2