Powerdrives Burning out Roboteqs

Hi

Having heard a few stories about Perm motors Technobot Power Drive motors buring out Roboteqs due to them causing huge voltage spikes when sudden reverse is used.

I was reading through the vantec website purely by chance and found this:
In this situation the batteries act as a voltage clamp protecting the controller. The battery chemistry must be healthy for this to occur. Dont add a series diode in line in the battery line because it will block the clamping action and the controller will fail. Some users place a large 100,000 ufd computer electolytic capacitor across the power going into the controller, a good idea, to further smooth the input voltage and clamping action.

Could this work with the roboteqs and possibly stop the problem?

Any ideas?

Regards
Ian

no.

No, as in: it wont stop the problem.

Roboteq and Technobots are still working to find a robust solution to this problem, a problem which we now understand. The voltage spike aspect has been resolved but the curent spike is being worked on. To give you some idea, we estimate a current spike in excess of 2200A being generated by the Power Drive motor in regen. Two solutions exist, either cope with this current or reduce the current. Once we have a proven solution, the Roboteq will take some beating in the world of DC speed controllers.

Paul

See, ask a question and you shall get a good and honest answer from the man himself.

Mike.

The Roboteq already takes some beating in the world of DC speed controllers!

Every pice of technoligy has its quirks. Theres no perfect speed controller, there probably never will be. At least not yet, mine is still on the drawingboard :)

Tanto can run the power drives :P

just a suggestion, could a 1 farad power cap from something like a monster car stereo install be used to absorb the backwash of current. These regularly see over 2000A in top installs.

not looked into this, just askin

No,

well it could. But that wouldnt really fix the problem.

James

The 2200A current is between the motor and the FETs, putting a cap like this across the motors would just be seen as a short circuit to the controller. Putting it across the battery would not resolve this particular issue.

Paul

Paul if u willing to replace the controller if you blow it up (not that they should) Im willing to let you try the 48330esc on power drives email me if u interested

6.3lbs weight!!!
1 channel
http://www.teamwhyachi.com/motor.htmhttp://www.teamwhyachi.com/motor.htm

Thats 5.7Kg of speed controller for drive!

yea and?

call it an insentive to loose weight

thanks kane/paul, as I said, didnt look into it, just something from the old boyracer days

Maybe a small device that monitors the voltage on the motor wires what will switch the motor leads to a something that will burn up this voltage spike when braking until the voltage drops back to a level that the fets will take and then connects the motor back to the controller? Im sure it could be done with a picaxe chip and some smart thinking. Just a brainstorm and Im sure someone will pick holes in the idea.

Euhmm.. hey youve got it all figured out :)
Im sure theyd have a solution if it where an easy fix.
Id try to use a higher switching frequency and a lower duty-cycle on regenerative breaking. But Im sure theyve tried all the easy fixes.
Maybe they cant upgrade the cpld contents with the normal firmware upgrade software.

You guys do realise that the maker of the Roboteq is working on this problem to produce a more refined fix!

Knightrous, the problem is current spikes rather than voltage. The Roboteq has built in hardware suppression against normal voltage spikes and additional means of isolating the motor from the output stages built into the software. Some spikes from low impedance motors like the LEM and Power Drive have so much energy and are of such short duration that even this protection is not adequate. Fortunately this issue has recently been resolved and works well.

The method of dumping regen energy into some switched load has been considered not just by myself but by other speedo designers I could mention and it is far from being a desirable solution.

Stefan, it is all about the duty cycle but a lower duty cycle is what is causing the problem at the moment. You need to be able to detect when in regen and also measure the regen curent in the bridge but very few bridge designs appear to allow for this. You are also quite right that the firmware upgrades cannot alter all functions, some are embedded as you suggest in the PLD which includes how the bridge is controlled.

We remain optimistic that a solution exists and I certainly do not mind suggestions, you never know it may just prompt a new thought process.

Thank you to those who have emailed direct with suggestions.

Paul

Following both successful bench and field trials (thanks to Dantomkia Mike), a new version of the Roboteq is now available - AX2550HR.

The development has also led to improvements on the standard version. A new version of the software will be available next week (waiting for me to upload) which will amongst a number of continual developments now feature regen current monitoring. What this means is that the controller will send a minimum of 25% of the regen current back to the batteries until it falls below a fixed threshold. Once it falls below this threshold, the controller will bring the motor to a halt. Effectively this means the deceleration ramps may be paused during periods of high regen current. This is very unlikley to be even noticed with motors such as the Bosch 750W, its there for LEMs and Perm Power Drives etc.

There is also a small hardware mod of 4 diodes to cope with spikes during regen. All motors generate these spikes and the standard Roboteq can cope with these for motors except the disc type LEMs etc. There is a risk that a faulty motor could also generate these spikes. These diodes are fitted to all units shipping from 1 Jan 2005 but can be retro-fitted to previous controllers.

Even with these changes, the disc motors (especially the Power Drive) still generate enormous regen currents so a new version is available that has twice the number of output FETs which means is can cope with twice the regen current as well as running cooler. Existing standard controllers can also be upgraded to the HR version.

It would be unrealistic to say that the Roboteq is now unbreakable, but surely it must be close.

See http://www.technobots.co.uk/en-gb/dept_332.html>here

Yipee!!!

Yeah - go get a Roboteq in Behemoth now Kane, learn how to drive with a good accurate control speed controller - no excuses now - you cant blame the 4QDs for your driving now, hehe.

Mr Stu

Bad news for me this weekend. I done gone and blown up my lovely RoboteQ. But before you lovely lot start feeling sorry for me let me tell you the tail of woe.

It all started when Paul C sent me the diodes for the modification that protects the HIP bridge controller chip. I duly fitted diodes and tested said unit. Other FETs were then fitted, new software, extensive testing and hey presto. A fully battle ready RoboteQ that safely handles the Powerdrives.

Well, I let Daniel drive Dantomkia and during the fight the smoke was let out of the FETs. Boy, does it stink !

There I was, looking at the innerds of the RoboteQ and to my horror I noticed the one of the diodes that I soldered into the board had come off. No diode on HIP means no HIP protection from mad bad Powerdrives. End result = expensive smoke and a very embarrised Mike.

Needless I still havent told Daniel this and he still believes that he did the deed. Come on, I need cups of tea you know.

Conclusion, solder diodes on correctly and glue gun them in place and RoboteQ will be bullet proof.

Now, just trying to pursuade Paul C that its still under warrenty!!!

Mike.

Ha, no chance of that Mikey, Ive got photographic proof that its YOUR fault!! Disclaimer duely witnessed and photographed for posterity!

So, how much is it worth not to tell Dan it wernt his fault...!!??

TTFN

Jon.

:) at last, a come-back to Mikes Welsh jokes.....

Check out my profile pic!!

Gotcha!

J.

Oi, thats not fair! cor, whats a man to do?

Oh well. As long as Daniel doesnt see this then tea is still free in my house. lol

And whats more? I shall tell you orrible lot a tale of woe.

This morning I was driving to work on the M25 and the engine was making a tinkling sound. Just like pinking. Well, I typically ignored this. When I got to work the sound was worse. Oh I thought. I put some oil in and started to drive home. On the M25 the engine started to sound quite bad. Knocking and banging all over the place. Well, just one mile short of South Minns service area there was a huge bang, the engine shuddered, there was a HUGE sound of shrapnel flying around the engine bay, the car then ran over parts of ejected engine and huge amounts of smoke came from the rear of the car as well as large amounts of engine parts.

Well, I made it to the service area and made a few calls to arrange to be picked up and have the car taken home ( £175 ) and then after a coffee to let the engine cool down I went to check on my baby. I was peering into the engine bay as one does when they know nothing about modern engines when I spotted this pretty looking piece sticking out of what remained of the fairly decent and well made engine block. I thought to my self, whats a pretty part like that doing there, so I stuck my hand into the engine block and extracted a borken and bent conrod. Oh well me thinks. This is going to be expensive. So far I have been quoted over £1000 just for the block casting and second hand engines start at about £950 ex vat etc.

Yep, tis expensive this motoring lark. BTW, the good news is that the oil leak that the engine had was repaired back in November by Toyota. Now thats a good repair me thinks. NOT!!!!

Poor and now skint Mikey. Donations to save Mikeys Toyota fund to reach me no later than 10 mins after you read this.

Mike.

Mike unfortunatly , but I could deliver another car, just 4 wheels and a motor, of course a steer on the wrong side for £370
Its a second hand Lada Samara.In good condition.An inheritance.

Ouch. Toyota didnt guarantee the work they did on it, did they?

£950 would be more than twice what I paid for my whole car :)

put a bike engine in it....that will do the same thing, ie blow up eventually, but at least itll sound nice

£950 for a car? Add a decimal point in there somewhere and youve got the price of mine.

As for weird engine noises, I find turning the radio up tends to cure them.

Steve, I did try that but even Meatloaf and Bat out of Hell loud enough to make the blood run out of my ears was not loud enough to cover up the engine noise.

Mike

quote:

so I stuck my hand into the engine block and extracted a borken and bent conrod
Was that all that was left? Not much to go on if trying to fix it methinks.
If the oil you put in this morning emptied that quick my expert :) diagnosis was that you didnt have a leak, it was a gaping hole. BTW what was the repair that Toyota allegedly made? Dont get rid of the old engine until you check what they did (thats if that section is still in one piece).

Heres a tip....... before you remove the old engine take off the oil filler cap and look down the tube. If you see something that looks like mayonnaise then your head gasket went. A thin coating is OK for this time of year but not if its thick.

Mike, I know its a Toyota Avensis. Is it a 1.8WTi by any chance?

no, a very expensive VVTi engine. Never let it be said that Toyota make cheap cars.

Look at my profile for a pic of poor broken conrod.

Mike

When do you get your CNC-mill? :)

next Friday.

BTW where is the big end? Have you found it? Or for that matter the piston?

lol, no idea where the pison is. maybe that was one of the items that I ran over in my haste to escape the scene of mass distruction.

The big end, or what remains of it is on my forfile. I know the pics bad but I know that you will forgive me. I cant be good at everything you know.

Mike.