K8055 - Dual Wiper Motor Control with Variable Speed

I can't think how that effect could come from the circuit alone (but need more information to be sure).
You will have to be careful putting twice the intended voltage through the relays - it will badly reduce their life before the contacts burn out, or worse, could damage the electromagnet in the switching part... 12v relays should not be used with 24V - get 24V ones!

All that aside, I think that the most likely cause of your PWM problem is your profile.

Remember that you have to send the dynamic value to the analogue output to make pwm work... check your settings in profiler, and compare with my profile in the first post in this thread... or just use my profile to get you started!

If that doesnt work, post a photo of your circuit, circuit diagram, and list of components - I may not be able to spot the problem, but there are plenty of electronics experts about in this forum!

Lastly, is it possible that your attempts with the boards before have damaged your K8055?
Full power could indicate that the PWM signal is not working / not being transmitted...
Try testing the PWM outputs on your K8055 in the interface section.
When you change the PWM settings in the interface area, the LED should get brighter for higher values set, and dimmer for lower values without actually going out for anything other than 0%.

Good luck!

Tim

Hi Tim

I have now got my hands on two (soon to be three) 160w 12v motors again from electric wheelchairs. I quickly hooked one up to check it worked :-
http://www.youtube.com/watch?v=qqDCB2TYrpU

James,who I got them from thinks they have either 17:1 or 25:1 gearing. I think I will try and work with the 12v ones like you suggested.

I had a look online for the Vellman interface and pre-built seems to cost around £65 If I want to control three motors then I assume I will need another board, do you know of any issues running two at the same time? In your originalpost you bought yours for £30. Can you recall where from?

Putting cost to one side just for a moment, do you think the pololu jrk12v12 boards would be more responsive and easier to configure for a numpty like me??

I took a look at the linear actuators...phew, a bit more work than I had in mind. Luckily, although I have already done a lot of the fabrication of the chassis, it is still adjustable as the rear cross members bolt in rather than welded (glad I did that now). So to make it work with motors shouldn't be too tricky.

I think i have more or less decided to ditch the idea of using scn5's, they are just too expensive, with the money I save on them, I can buy 3x 42 screens and a 5870 graphics card.

The other thing I have yet to get my head round is creating the game profiles. Can you use other peoples profiles even though the design of your rig is different to theirs?

Thanks for all your help so far :

Deaks

Hi Deaks

I got my K8055 straight off the shelf from Maplin. It was on special, and they were doing the prebuilt for the same price as the kit to build yourself... which is really really complicated! The extra £10 is well worth it! Current prices according to the website are:

USB Experiment Interface Board
USB Exp Int Board, N67BH, £29.99
USB Exp Board Assm, L92BL, £39.99

I am biassed against the Pololu boards - for no other reason than the cost... I'm sure they are great... just very expensive!
The relay solution I have been developing is simple, cheap and effective - and if it does go wrong, or dies on you (which is unlikely as it is so simple and robust with no static sensitive mosfets etc) you can easily and cheaply replace it.
The sheer cost of the pololu boards would make me very nervous about experimenting.

I think you are right to ditch the scn5s for now - they ARE awesome, but very expensive and apparently quite sensitive to twisting...

On the profiles, the honest answer is that I don't know... yet!

It is easy enough to map an axis to a motor, but as to blending axis data across two motors (or more) that is a part of the journey that I still have to make! Some of the profiles on the site from other people may be suitable, but not many have used my solution so far - most of the profiles are for Tronics setup... Whatever solution eventually comes out of this, my intention is to keep pushing the envelope and increasing options for anyone starting out.

I am intending to use 2 K8055s (and yes that is supposedly possible, but you have to make a registry change to allow the system to start the second board) and build a floating platform with 3 actuators (just like RolandVanRoys) with 2 of the actuators blended to give roll, and the remaining one taking pitch movements.
I don't know for 100% certain that it can be done... watch this space - I like a challenge

Let me know how your build goes - I'm more than happy to help out if I can!

Tim 8)

Thanks again Tim

I didn't even think of looking on the Maplin site as they are usually pretty expensive, certainly for CAT5 cables and AV stuff. I usually get my bits from CPC.

I was in Maplins this afternoon getting some solder, I could have got one then.

Deaks

nice motor. seems like faster then wiper..

@Bigtalltim
Can you please look , how much Volt coming out from the PWM Pin with different settings (0-255).
Is the 1K Resistance wrong when using 24V?
I think so.
But which Resistance should i take?
Im a very big Noob in electonics.
My Transistors are signed as: BC548C

Ok i finished here.

Now my K8055 is burned of.
Thats all for me with self construction.

Hi Menix

I think you misunderstand how the pins on the K8055 work

They are effectively pull down inputs - they do not have a voltage output as such.

The Velleman forum has good explanations of the way they work - definitely worth reading in detail before giving up...
Depending how you are measuring, and what you are expecting to find with your voltmeter, your K8055 may be OK - just operating in a way you do not expect.

If you make exactly as I have shown with only 12V, it will be a good start. Then you can upgrade the components in stages - I think you have just tried to do too much too soon and combinations of problems have made it difficult.

I hope you do not let these set backs put you off - I had many problems myself in the early stages... just research the problems one at a time, and work around them!

Good luck

Tim

Sorry
but i destroeyd my H-Bridges and my K8055

Now i ordered this Board
http://www.watterott.com/de/Arduino-Duemilanove

and this H-bridge

http://www.watterott.com/de/Dual-Motor- ... SP30-MD03A

For a new Test

Fair enough Menix - I hope it works out for you!

never let a set back hold you back

Good luck!

Tim

I would tried this first...
http://www.watterott.com/de/Motor-Steue ... 8734-18v25

Its a bit expensive but I guess it worths cause of the double mosfet pairs...

Or this that has on board Current sensor too... :brows:
http://www.watterott.com/de/Motor-Steue ... 4-18v25-CS

Actuators

I finally got the prototype of my wipermotor sarrus linkage actuator built! :yippiee:

All that remains is to get the bungee cords attached (I will probably increase the width to get more cords in) and make another 2 of these... the floating platform concept seems to be almost within reach!!!

The total cost including the bungee, AND the wiper motor, will be no more than £15 to £20! - as usual, cost is one of my major considerations with this project.

This actuator uses the bearings from skateboards (£0.30 each) and is otherwise made of cheap plywood - it seems strong enough, but I may go for a full metal construction in the end.

http://www.youtube.com/watch?v=BgF1j-KQrXo

For anyone interested in how this and Roland VanRoys actuators work, here is a video explaining the core design principles.

http://www.youtube.com/watch?v=LoN6CnaUxdc

It's starting to feel like the end is in sight!!

Tim 8)

Great work as always Tim!

The extra linkage in my opinion just overcomplicates the geometry and limits your range of motion. If you connect the wiper directly to the main arm/link, you will still have your feature, but you are not limiting that range of motion to ~45°. Play around with different positions and lengths and you will see what I'm talking about.

Cheers Frakk!

The reason I had to go with the extra linkage is because of the one weakness in this solution that I can do nothing about without a change to the relay board - if the software crashes, the motor hits max speed and just keeps going! (This is because it is the PWM signal that limits and controls the speed. If the board crashes, the PWM channel stops working...PWM = 0 which means Max speed).
In fact I am currently reworking the relay solution to include breaker switches on the extremes of position, so it will be impossible for the actuator to destroy itself without the extra linkage...

Also, by moving the vertical arm closer to the fulcrum, I am able to achieve 150mm of vertical movement, which is enough for now...
the prototype has only 100mm of vertical movement.

I started off with the motor attached directly to the drum holding the bungee as you suggest - the problems became very apparent when I was fiddling with the profile and the first crash happened under test - the motor just keeps going, and tightens the bungees to the point that something dies or snaps... like over winding a clock spring only much more destructive!.

With the motor setup like this through the extra linkage, that cannot happen - the worst that could happen is a very VERY bumpy ride for the operator, before he manages to pull the plug!

The other nice thing about this setup is that whatever the position of the arm, the vertical bar is always loading the bungee, so there is no position where the motors are over loaded by operating without spring assistance - if the driving arm had more than a 90 degree sweep, there would always be a point where the weight of the arm is directly over the bearing, or hanging from it, and the spring is not loaded by gravity.

It took ages to get a position for all the joints that worked, and I tried many configurations - thats why the prototype in corex board looks like it has been shot with a scattergun! - but this was the configuration that offered the best oportunity for development with the Relay board in its current state

Tim

@Frakk

I forgot to say: the video only shows a movement from 20% to 70% and back in the positive range

Tim

That is good thinking! Bungee cords are great, but I wouldn't stop there. Have you thought about a vertically loaded spring under the final linkage?

That will eliminate all of your worries. The spring will compress according to the vertical position of the actuator, and not connected to any rotational parts that would destroy it.


To solve the issue with the PWM signal, you just have to invert it. When software crashes, everything 0V, transistor completely OFF -> motor doesn't have power anymore.

Now theres a superb idea! - The bungees would be more easily adjustable for different riders, but a spring would allow for a much smaller actuator - more along the kind of scale of a blue tiger... :yippiee:

I have a mate who fixes bikes, so getting small suspension springs from a bike or moped should be easy... then I just have to design an adjustable mount for it - I have some ideas already

Watch this space!

: Cheers Frakk!

Tim

Hi Frakk - it's back to bungees after all with this design!

When measuring to identify the correct spring rating and overall dimensions, I have discovered a problem that I had not anticipated!

I have designed a spring mount that would be absolutely perfect if the frame was fixed and the joint was to operate only in the vertical range, or if the horizontal arm was fixed... however...
as the design of this actuator is to be used as one of a set of 3 arranged in a triangle, and the movements of either of the other two actuators will affect the vertical position of this one relative to the central spindle, springs aren't going to work quite as expected... this picture illustrates the potential range of movement:


(the screenshots come from Rolandvanroys video as linked in the thread earlier)

There is a suprising amount of variation in the position of the top and bottom actuator arms - the springs I would need to be looking at would be significantly affected by a 2cm variance in position, meaning that the frame would move disproportionately in the vertical range. These pictures show the range of movement over quite a small horizontal range with the motor fixed in the same position





Because the bungees are fixed to the central spindle which is not moved by input force from the other actuators, they are able to support the actuator in a fixed vertical position regardless of the movement of the rest of the frame.

I am still looking at other designs for linear actuators that will be able to make use of the spring mount though, so will keep that one in the bag for now

Tim

I don't see any problems here. The spring/shock cannot be fixed at a 90° vertical, it has to pivot with each actuator.

Red and Blue are two options to mount a spring shock. The spring rate can be easily estimated. Ex. you have a 300lb upper platform = 100lb on each actuator traveling 4.
Travel/Weight = 25lb/in = Spring rate. Adjust the preload to set neutral ride height and away you go.

The biggest problem might be finding the right parts as the shock has to be matched for the actuator geometry. An other solution would be to use air loaded pistons, in that case you only have to worry about the size, the spring rate can be adjusted by air.

That was my first thought too... we are totally on the same page here!

The problem is that the actuator arm works like your arm - As you flex your biceps, your wrist moves closer to your shoulder... as you flex your tricep, it moves further away. Locking the position of the wrist relative to the shoulder compromises both bicep and tricep (depending on which way you want to move your arm).

The following pic goes some way to showing just how much movement comes from the arm in use:



My spring mount design is simple: it has a central shaft fixed in position, and a top connection through which the central shaft passes -just the same as the suspension leg in a car. It connects just as you suggest (except not to the very end... instead, to halfway along):



The problems come with trying to find a spring with enough power to support the frame, that will allow a 20mm variance

Please correct me if this calculation is wrong, but as I understand it, if the spring (linear) has a free length of 100mm and needs to compress to 50mm to support 50KG, the loading is approximately 10kg per 10mm of movement. this means that the 20mm of movement is like changing the weight on the platform by 20kg, and also that the wiper motor arm is going to have to produce huge forces to be able to further compress the spring to move the platform up or down beyond this central point - the range of movement of the wiper arm gives about 40mm movement in either direction... with the amplified movement of the disc, and adjustable position of the vertical arm on the horizontal one, this becomes 50mm or more. Working still on 10Kg per 10mm, I think a sustained 50Kg force or more would be beyond the wiper motors I have...

I am still looking into springs for linear applications, but for this actuator, I dont think I will find a commercially available spring that would work out.
That said, because you are so sure this will work, and I am not 110% confident that it wont, ...I'm going to try it anyway!

Because I have no springs yet, I have been working on a way of minaturising the bungee arrangement this afternoon - kind of like a compound bow...

I will be catching up with my bike mending mate over the next couple of days to see if any of his old parts will fit the bill

Tim