Micro1895 and 1530/7 can't start???

[djey]

I recently receive a 1530/7 Hi amp that I plugged to my BK Micro1895
I have a small problem of power cut when I going from no RPM to full trottle
in one time.
(Motor wasn't mounted in anything (no load at all!!!) and Batteries were
Full charged GP3300 (6cells) on a Schulze 330d charger...)
All good material!

I ofen use my controller with a 1930/10Hi amp on 12 cells without
problems...

I'm not the only one to have this problem (2 other guys avec the same
problem with Warrior9918, LMT1530/7 and 6 cells).

The problem looks like a Phase lost (or bad motion control) when accelerating quickly from no rpm (or few).

Does anyone has a solution??? :confused:

Thanks
Djey

[studysession]

Does it work fine when you start off slow?

[mac0326]

Try it with a receiver pack. It sounds like the older warrior controllers (a couple years ago). The problem was BEC related and was fixed with a receiver pack or UBEC. Higher cell counts fix the problem, too.

[djey]

Try it with a receiver pack. It sounds like the older warrior controllers (a couple years ago). The problem was BEC related and was fixed with a receiver pack or UBEC. Higher cell counts fix the problem, too.

Yes people told me to try with it. I'll try it as soon as possible.
With 12 cells I have no problem on the 1930/10 but did not test with the 1530 (I'll do it and will limit rpm manually).
For information : new Warrior 9918 have exactly the same problem when running under 6-7cells (we didn't try more).

studysession : yes it start when starting slowly. The problem also occur after cornering at low speed (180° or tight Left - right - left for instance).

[666yeti666]

djey,
maybe you should program the micro1895 with "start-up protection" DISABLED. According the manual it's preferrable to do so because of the high current draw during start-up, specially at 6 cells and using the BEC.

[djey]

djey,
maybe you should program the micro1895 with "start-up protection" DISABLED. According the manual it's preferrable to do so because of the high current draw during start-up, specially at 6 cells and using the BEC.


I tried all programming options and it doesn't change anything. But this morning I tried with a RX pack and this seems work great.
It doesn't cut anymore :D

thanks for foru help
Djey

[studysession]

djev - I have experienced the exact same problem. Even had it happen when turning like you stated. Problem is the low voltage cut off. When running with an RX pack, that has helped me in few times. This is why I like the Castle Creations products. You can set the low voltage cutt off to zero, so this won't happen. While other ESC's they try to autodetect # of cells and the ESC uses that to determine what the minimum voltage it needs to run. When you go full throttle it require more draw off the batteries and what the ESC thinks the current charge of the batteries drops so it coggs or stops running all together.

Personally I wish all manufactures would put a way to shut off the low voltage cut off like the castle creations.

[666yeti666]

Djey,
yesterday I faced the same problem and found the same solution. Just put in a seperate receiver pack. It works, although it's not a nice solution because of the weight increase.
I sent an email to LMT, asking them for a more subtle solution, so now just waiting for the answer.

Another solution could be, adding 1 cell to the 6 cell package. Maybe then the voltage decrease will be just above the shut-off level (3.2 Volt in CAR modus).

[mac0326]

You could also install an external BEC like the UBEC (http://www.rc-monster.com/proddetail.php?prod=6vubec&cat=21). This unit weighs less than an ounce and will accomplish the same thing as the receiver pack.

[starluckrc]

Better batteries definitely help. My 2 cell lipoly works great.

[666yeti666]

mac0326,
that's a very good option ! That I haven't thought about it !
But I'm gonna make one myself, just by using a LM7805, an electronic component that puts out 5V , for less than a dollar :-) Only 2 extra capacitors are needed to make it work. This week I'm gonna make one.
Thanks for the suggestion !

[starluckrc]

I don't see how the UBEC will help on 6 cells. It is fed by the pack that is dropping voltage under load. The UBEC will just go into bypass mode when the voltage drops and the controller will see the battery voltage. On higher cell counts, it will help.

[666yeti666]

starluckrc,
the BEC of the CONTROLLER needs a minimum input voltage for proper functioning (becuase of voltage drop across it). So when the controller reaches it's minimum input voltage, the microprocessor switches it off, while the UBEC has the possibility to "pass" this voltage to the controller, which might be just enough voltage (& time) to keep the microprocessor alive.
But of course it has to be tested in practice.

Maybe I will face the same problem with the lm7805, it needs a minimum input voltage to function properly. On the other hand, the voltage drop is only visible for some milliseconds, so it might be enough to buffer the voltage with a large capacitor at the input of the regulator. Or using a low drop regulator.

[TheSteve]

The 7805 is really a poor choice for a BEC, they do work but the nature of the device means they have excessive voltage drop - as in they need more then 6 volts just to maintain 5 volts on the output. A more suitable regulator would be something like Novak uses in high-end controllers like the MIC29302. On the output of the BEC circuit you could add a Novak "stutter stopper" or just add your own .1 to 1 Farad 5.5 volt capacitor(these are very small and will do the exact job you need) This also means you shouldn't set the BEC voltage to more then 5 volts as it would be bad for the capacitor. Hope it works!

[666yeti666]

Steve,
thanks, I could not find the minimum input voltage in the datasheet of the 7805. In this case, indeed a low drop regulator is a better choice. About the 1 farad cap, when it is empty and connected to the battery for the first time, it draws a very large chargecurrent through the regulator, maybe it doesn't like that.

[TheSteve]

I think the capacitor charging through the regulator would be fine. The smaller high-value capacitors don't have a really low impedance, so they don't charge super fast. You could also stick with something a little smaller like 0.1 to 0.22F. Regulators are usually fine with a high inrush of current because its such a short period of time.

[starluckrc]

That's what I'm saying.....once the battery voltage drops too low, the voltage on the UBEC is too low as well. The UBEC doesn't make voltage.
BK fininally posted a capacitor mod for the rx on their website.

[glassdoctor]

Have you guys seen Novak's new BEC circuit? I just called them and left a message asking about max voltage input. Haven't heard back yet.

www.teamnovak.com under new products on the front page...

It uses the same mic controller you mentioned... it's $17.99 at tower

http://www2.towerhobbies.com/cgi-bin/WTI0095P?FVSEARCH=nitro+servo+regulator&FVPROFIL=++

[glassdoctor]

Just talked to someone from Novak. He said they don't recomend using it with more than 7cells/2s lipo... higher voltage = less current delivery. So it would be a great bec option for 2s lipo packs.

If I run 4s lipo packs, I might use one and tap into the voltage from each 7.4V pack. But it won't work for 3s packs...

[666yeti666]

starluckrc,
indeed, BK adviced to put a 1000 uF on the rx.
I will try it as soon as possible and will let you know the result.

[666yeti666]

Hi,
I just tried a capacitor of 4700uF on the free rx connector and it didn't work out !


I'm using it on a lehner micro1895 and a basic 5300 in a 2 wheel drive duratrax evader truck with masher 2000 tires (18 pinion, 88 spur) with a 6 cell sanyo 2400 pack.

Maybe it does work out on a warrior controller, but to be honest, I doubt it very strong ....
What do you think the extra capacitors on the controller are needed for ....