Crystalyte Controllers - Repair and Modification information

[Jozzer]

Thank you Bob, helpfull as ever

[bobmcree]

i don't want to dissuade anyone who wants to rip out spokes and do wheelies, it is fun. people who don't desire this should read the following:

we should consider that doctorbass has upgraded his controller to fets that can handle 16x the power of the standard ones, so the fact that he has not blown them cannot be taken as an indication that the same mods to a stock controller start up cap would have the same result.

there is a good reason for the soft start cap, and just because the crystalyte designers took shortcuts to save a buck does not mean it can be disabled or treated lightly. there are many good reasons not to instantaneously apply full pwm to the fets when the shutdown signal is de-asserted. if you shorten up the time constant that applies to every startup function, and there may be cases where the ebrake or low batt signal is asserted that you do not want the system to jump back to full power as soon as it is released. i really think it is a better idea to decrease the resistor value that charges the cap from the throttle signal, preserving the soft start function for power-up and ebrake release.

[rf]

Can someone tell me how to locate the current limit adjustment resistor on the 48volt 20amp controller?

Thanks

Richard

[fechter]

From a schematic standpoint, it will be the same as the 35 amp version.
See page 1 of this topic.

I've never actually seen a 20 amp one in person, so I don't know the board layout.

You should be able to trace it out from the KA2535.

You could also just change the shunt if you don't need an adjustable change.

[Jozzer]

http://endless-sphere.com/forums/viewto ... t+limiting
Pic and instructions for 20A version. The other Fechter knows the board layout

[rf]

Can someone tell me how to locate the current limit adjustment resistor on the 48volt 20amp controller?

Okay, I wasn't explicit enough.

I have a CycleAnalyst, so I don't need variable current boost. What's the easiest way to up the max current on a 20amp controller without disturbing the shunt itself?

Thanks

Richard

[bobmcree]

it is much simpler to change the shunt resistance than any other method, either by adding solder to connect two of the shunt conductors together for part of its length or by soldering a piece of wire between battery minus and the minus of the big caps. if you use a piece of #10 wire about 8-10 inches long you can bring it out of the controller and connect the ends together externally for more current, and adjust the wire length to get the desired limit.

because of the way they do the current limiting and low batt by hijacking the error amp in the ka3525 it is difficult to do it repeatably by any other means.

if you have a current limited power supply and a good meter, you can run an amp or two through the shunt on the controller, and you should find it is very close to a milliohm, inferred from the 1 mv/amp voltage drop across it. you can add solder until the voltage goes down to about 80% of the original value, then reprogram the cycle analyst with the new shunt value.

because of nonlinearity in the circuit the change in the shunt will not give you exactly the boost in amps you would expect from the resistance values, more like the square of the change you make is my experience. (if you make the shunt 70% of the original value it will about double the current limit). the adjustable current limiting methods that have been posted rely on first increasing the current by modifying the shunt.

[rf]

it is much simpler to change the shunt resistance than any other method, either by adding solder to connect two of the shunt conductors together for part of its length or by soldering a piece of wire between battery minus and the minus of the big caps. ...

That sounds like the easiest way, except I gather from what others have said here, that will make my CycleAnalyst's current readings inaccurate. Is that not the case?


Thanks

Richard

[rkosiorek]

not really. as i understand the instructions, you have to measure the value of the shunt resistor in your controller and enter the value into the setup regardless. the only time you don't have to do this is if you buy the controller and Cycle analyst at the same time. then they calibrate it for you.

rick

[bobmcree]

rick is correct. the controllers i have measured are within a few percent of the .001 ohm default in the cycle analyst, but the value is totally programmable. you can measure the value before and after the mod by passing a known current between the negative battery lead and the minus end of the big electrolytic caps, and then measuring the voltage across the points where you connected the cycle analyst sense leads to the shunt.

if you have a 1A supply and the voltage across the shunt is .001v that would be typical, and to go from 20a to 30a i expect you will want to reduce the shunt by 20% or so for the first cut, so add solder to half the length of 2 of the conductors and re-measure the voltage across the shunt, then scale the programmed value of the shunt by that factor.

alternately, if you have a good ammeter you want to use for transfer of calibration, compare the cycle analyst readings with those it provides, and scale the default shunt value of .001 ohms by the reciprocal of the ratio you measure to correct the readings.

[rf]

... alternately, if you have a good ammeter you want to use for transfer of calibration, compare the cycle analyst readings with those it provides, and scale the default shunt value of .001 ohms by the reciprocal of the ratio you measure to correct the readings.

Thanks Bob. That sounds good. But won't modifying the shunt with solder or whatever make it nonlinear? Or will calibrating to the middle of the range be good enough?

[rf]

It just occurred to me that modifying the shunt is kind of questionable. If I'm using the CycleAnalyst as my current limiter then messing with it's current sensor is probably a questionable manuever.

Perhaps the resistor network is a better idea. Assuming that won't change CA's readings ...

Richard

[bobmcree]

... alternately, if you have a good ammeter you want to use for transfer of calibration, compare the cycle analyst readings with those it provides, and scale the default shunt value of .001 ohms by the reciprocal of the ratio you measure to correct the readings.

Thanks Bob. That sounds good. But won't modifying the shunt with solder or whatever make it nonlinear? Or will calibrating to the middle of the range be good enough?

it is just a resistor so there is not a problem with linearity. there is the issue of temperature coefficient, but even if you just use copper wire in parallel with the existing shunt the tc of copper wire is about 400 ppm per degree C so if the wire varies in temperature from freezing to boiling water that is still only a few percent error, and it is only part of the shunt so the error due to temperature is not really a problem.

i keep meaining to fill in the couple of gaps in the schematic, and try to figure out a way to use the error amp in the KA3525 to implement a true current feedback throttle. it should be possible with just a few hacks to the pcb and maybe an added op amp.

i am getting continuing requests to bump up the current limit on the controllers i am refitting with the 4110 fets, since they seem to handle 80A or more quite reliably. i will be doing a couple this week set for as close to 100A as i can get, and will post the details. of course anything over 50A I will not warranty except not to be DOA

[bobmcree]

you can always get the external shunt for the cycle analyst or make your own, so that the measurement will be independent of any controller mods. the new ones justin is using have a much better temperature coefficient, but i think they are really only intended to take 50A or so. the stock shunt is made of wire that does not seem to be anything special, and i have seen them wander around by several percent over normal operating temperature. they also have some galvanic issues, voltages created by joining dissimilar metals. adding more solder to the system does not seem to make these problems any more pronounced.

i have replaced the stock shunt resistors in a couple with some kelvin connected resistors that look like little sawhorses. the current goes through 2 legs and the voltage is sensed across the other 2, greatly reducing error.

i know a guy who is routinely increasing the current limit as high as 80A by adding the parallel piece of heavy copper wire and varying the length. this seems to work fine for him.

[fechter]

http://endless-sphere.com/forums/viewtopic.php?t=915&highlight=current+limiting
Pic and instructions for 20A version. The other Fechter knows the board layout

Geez... I guess that brain cell died somewhere along the way.

If you change the 51k resistor in the schematic to something like 25k, you can boost the current limit without changing the shunt value (so the CA will still be accurate). If you go too high, the shunt could overheat.

[rf]

http://endless-sphere.com/forums/viewtopic.php?t=915&highlight=current+limiting
Pic and instructions for 20A version. The other Fechter knows the board layout

Geez... I guess that brain cell died somewhere along the way.

If you change the 51k resistor in the schematic to something like 25k, you can boost the current limit without changing the shunt value (so the CA will still be accurate). If you go too high, the shunt could overheat.

Cool! Thanks.
Decent ammeters are expensive ...

[fechter]

25k is a wild ass guess. Be careful messing around with that one, since you could easily crank the limit up to self-destruct point.

[rf]

25k is a wild ass guess. Be careful messing around with that one, since you could easily crank the limit up to self-destruct point.

No problem. I'll yell Yippee-Kai-Aye when I test it.

[Roy]

I've got the old FET's out of my 20a controller board and
have done my best to soak up the excess solder. But... the
holes are just too tight to allow the replacement 4110's to fit in
properly. Right now I'm considering: Filing the FET leads to make
them skinnier (sounds insane), tiny drill to open up the holes (likely to tear the trace?), clamp a paper clip to the tip of a solder gun and force it thru the
holes melting solder along the way. etc. Only 2-3 out of 18 holes are adequate to allow the new FET's to install easily.

Suggestions?

Thanks,
Roy

BTW, how does one get the privilege of starting a new topic?

[bobmcree]

the holes should be big enough for any TO-220 fet. have you used solder wick to get the last of the solder out?

the next step is to enlarge the holes with a sharp probe or drill. they can be soldered on both sides of the board so you do not need to rely on the through hole plating to carry the gate signal through, and the power leads must be soldered to the side where the bus is anyway.

be sure to use plenty of solder on the drain and source connections, as it is really the solder that carries the bulk of the current

[fechter]

Solderwick is good for clearing the holes.

Another method is "heat and beat". Heat up the solder, then quickly whack the board against a table or something to fling the solder out of the hole. Just be careful not to damage any of the protruding components.

This is about the only way to clear solder from a solder cup type pin on a connector.

Good luck.

[Roy]

the holes should be big enough for any TO-220 fet. have you used solder wick to get the last of the solder out?

the next step is to enlarge the holes with a sharp probe or drill. they can be soldered on both sides of the board so you do not need to rely on the through hole plating to carry the gate signal through, and the power leads must be soldered to the side where the bus is anyway.

be sure to use plenty of solder on the drain and source connections, as it is really the solder that carries the bulk of the current

I don't think I can wick much more solder off w/o more trace damage. I will make sure S/D get plenty of solder.
Thanks,
Roy

[Roy]

Solderwick is good for clearing the holes.

Another method is "heat and beat". Heat up the solder, then quickly whack the board against a table or something to fling the solder out of the hole. Just be careful not to damage any of the protruding components.

This is about the only way to clear solder from a solder cup type pin on a connector.

Good luck.

Yikes! Don't think I've the spunk to try "heat and beat". But what do you mean by "solder cup type pin"? To me these are just holes in the PC board. I've got a probe made from a bobby-pin that is flat like a component lead. Made by filing it down to a tapered end. That's my next try.

Roy

[fechter]

Solder cup pins are like the kind installed in many connectors. Not usually found on boards. Since the "cup" is closed at the bottom, there's no way to vacuum out the solder.

Anyway, the bobby pin should work. I sometimes use a tiny screwdriver like a drill to ream out the leftover solder. Just try not to destroy the copper or lift the traces. Like Bob pointed out, if you rip out the plating that goes through the hole, you can fix that by thoroughly soldering the lead on both sides of the board.

[TylerDurden]

Sometimes you can use a can of dust-off (compressed-air) to blow out the hot solder.