K8055 - Dual Wiper Motor Control with Variable Speed

Mixed success tonight - I have the prototype built, and it is very strong, but I think my pot is damaged as it is very twitchy.

Will get hold of a new pot tomorrow and try to post a better video demonstrating the power and control

Tim

No luck getting a new 10K pot today, so unfortunately no satisfactory prototype this weekend.

Got the electrics sorted, and the protection switches rigged - just need to change that pot!
I definitely need to do something more elegant with the pot mounting too...

I'm only working away until Wednesday night this week, so will get back on this on Thursday evening

Heres the jittery first test for now - it is pretty ropey so far, and there is no sarrus linkage - from the pictures posted before it should be easy to see how the final arm attaches and how the basic actuator principle works... it is likely that I will include another set of gears below the wiper motor set to give more power

http://www.youtube.com/watch?v=8ovfgd5clxg

Tim

for sure jewelryab - go for it!

Everyone can help others by sharing ideas, methods and mechanisms -its what makes this forum such a fantastic resource :thbup:

Tim

Hi after another long absence!

I have now built and am testing my motion platform, but am waiting on some multiturn 10K pots (10 turn) to arrive from the far east so that I can set up and demonstrate it properly before posting videos (the standard ones I had didnt have enough of a range of motion)

It is different in construction from any other that I have seen, and I'm not sure how it will perform when wired up so bear with me - certainly there is loads of power... it is kind of similar to deriys platform, but has a huge range of movement and far more power due to the actuator design

My latest actuator design is (I believe) completly unique - so I'm keeping my cards close to my chest until I have it perfected...

Work is still crazy, but I have a holiday in 2 weeks, so will have it completely finished and posted by then!

Tim

Tim,
This is some AWESOME stuff you have going on here!
In your Discussion entitled 'Connecting Position Indicating Pots to K8055...' you describe and show a single pot. From what I can see on the board there is only one connection for a positioning pot.
Does that mean that if I want to control both X and Y (or pitch and roll), I'll need two K8055s?

Tim - I read on page 19 that you indicate the board can support 2 positioning pots. :thbup: That's the way I'm gonna go!

Thanks again for this.

Hey Tim, glad you are still working on this and I look forward to seeing your completed platform.

I've taken some time and, using windows paint, transferred the mosfet relay circuit design to a pcb board layout.

I think I got everything correct, but if someone has time, perhaps they can confirm it for me.

The one I don't know is what type of Schottky diode I should use.
Here is the basic circuit:


Here is the board back (This is confirmed to be to scale):


Here is the board front (silkscreen) (This is also confirmed to be to scale):


I plan on etching them soon...

Tim,

Is you power transistor BUX127 still recommended? I can't seem to get my Sabertooth to do what I want and I was planning on building your circuit.

Thanks,
Dave

Hi Dave

As you read through the thread, you'll find a number of alternatives that have been suggested - Frakks mosfet solution is probably the most serious alternative, and specs were suggested for a shopping list of standard commonly available components....

that said, for a static safe super cheap and robust solution, try the BUX127!

If I'm honest, the reason I went with them is that I had some in a maplin lucky bag of mixed components, but nearly a year on from my first build, I'm still using the same components (as in, never had to replace them).

Under load they can get quite warm so a fan is a good idea, but I can confirm from personal use that they are completely adequate for the job :thbup:

Tim

Hi - yes... still working on this, and on holiday this week... so I WILL have something to show really soon!

Tim

good stuff - many thanks for doing this!

I haven't had time aside to test this alternative myself (posted early on in the thread by Frakk) and would be really interested to see how it performs!

Tim

I think this is how I would connect to the K8055 to the relay circuit.

Is this correct?

Second question:
In the upper right of the board you have a 12V. On the bottom right, you have a -VE.
I know the 12V would connect to an external 12 V power supply.
What does the -VE connect to?

Thanks.
Kevin

Hi Kevin

Q1. In a word, no...

K8055 D/O1 is Digital Out 1... At the bottom of the right hand edge of the board, not shown in your diagram and labelled 01 (though you can see D/O8, D/O7 and D/O6 on your diagram (labelled as 08, 07 and 06 under clamp)

Also, I use the Gnd directly above clamp though this is less important.

That would be the negative terminal of the 12V battery - or in my case, the black wire in the molex connector... the yellow wire is the +12V

Hope that helps - anything else, just drop another post! :thbup:

Tim

Thanks for the clarification.
I have one (actually two) more questions.


1. What type of transistor could be used here?
2. What ohm value of resistor should be used?

Sorry for all the questions, but once I have this info, I'll upload another pcb image for this layout

Thanks,
Kevin

Hi Kevin

check out Page 12 post 9 of this thread where both are specified :thbup:

The diagram you are looking at is my illustration of how the circuit layout differs... its intended use is for 24V, or relays that draw more current through the coil than the K8055 inputs can take... you may find that the leg layout for a suitable 24V DPDT relay is different - I have not used this circuit myself as I am sticking to 12V for PCU power unit convenience!

All resistors are 1K, and the transistor is a PNP 2N3906

If you are going to design a PCB for this circuit, you will need to specify also a suitable relay for the 24V, download its data sheet, potentially redesign the leg layout and after all that, if the coil current is within tollerance, you may find that the extra transistor is not needed!
(the K8055 contacts are rated for a maximum of 50V @ 100mA...)

Breadboard for prototyping first is probably the way to go

Tim

I have a couple questions:
1. In the image below, I am inferring that the Collector, Base and Emitter are as I show with C, B and E.
Is this correct?


2. This post from the velleman site indicates that a 2N6284 should be used instead of a 2N3055 for Q1
http://forum.velleman.eu/viewtopic.php?f=15&t=3839&start=30

Does anyone have any thoughts on this?

Thanks, Kevin

this depends on your selection of components - leg layouts vary... you need to download the datasheet for your chosen component (just google the component code) - it may be necessary to change the track layout around.

As long as the component is of the same type and of a similar or greater spec, it should be fine - you just have to watch out for the leg layout... I havent checked the datasheets, but it is likely that these components are very similar.
If in doubt, I would suggest that the circuits and components specified by the board manufacturer themselves are probably a pretty safe bet!! :thbup:

Tim

OK - that makes sense

But this is the correct connection, right?

Hi Kevin

The leg layout you showed in your diagram was wrong...

the most important detail is that the K8055 PWM connection (and resistor) connect to the base of the transistor.
Check out the description on Page14 post 9, where I explained how the solution works - that will help you to understand how the K8055 contact controls the base of the transistor to switch the power on and off

Off the top of my head, the leg layout of the circuit from top to bottom (using a BUX127 ) should be B, C, E... your diagram (shown below) shows E,B,C... it should be easy enough to find the data sheet on google to confirm this



Tim

here you go Kevin - not the best picture in the world, but it will do...

Found this at http://english.electronica-pt.com/db/cross-reference.php?ref=BUX127



Tim