Greentime LVC

[ian.mich]

how do i mod the LVC on this controller? i found the VCC, and there is one open spot for a 2nd resistor that i pointed at in the picture, do i just add a 2nd resistor to raise the LVC? i've been reading the generic controller thread all afternoon but can't make sense of it, they said to put a resistor between the VCC and the GND, which is possible, but how do i set this up then? i drew out how the juice flows. Edit: I think putting a 2nd resistor there would lower the resistance (i believe it would make them be in parallel and resistance in parallel is (1/r)+(1/r)=rt). But still not sure. there is also a blank spot with two adjacent blobs of solder, above and left of the VDD. sorry about the crappy picture dont have a great camera



better picture

[ian.mich]

This has me stumped. then again, im no EE

[HypnoToad]

This has me stumped. then again, im no EE

Me neither, but I'm trying to do something similar to you, I'm trying to change the HVC on an eZee controller, as it's made for 36v and I'm using a 48v battery.

Here's what I've done so far, I think I'm almost there: First I found the main microcontroller chip, it's a PIC16F73 in my case.

Then lookup the datasheet and find the pinout, here's mine:



Pins 2,3,4 and 5 are of interest here, they are analogue ins.

What I did next was to vary my battery voltage in even steps, and measure the voltage on these pins. If you are lucky, 1 pin will vary evenly with input voltage. Here are my readings, and pin2 on the PIC16F73 was my pin that changed in proportion to battery voltage:

Battery voltage / Pin 2:
40.4v (10s) / 3.657v
32.36v (8s) / 2.923v
24.31v (6s) / 2.196v
16.23v (4s) / 1.468v
8.07v (2s) / 0.731v

Now I already know that the LVC on my controller is 28v and the HVC is 44v, and this equates to the voltage on pin2 being above 2.5v and below 4v.

What I'm doing now is trying to trace back the resistors which are in series with pin2, and I'm going to try and change the resistance so that an input battery voltage of 36v produces 2.5v on pin2 for the LVC and a battery voltage of 53v produces a voltage of pin2.

This should work in theory, but I've never done it before, so don't take my word as gospel.

Try and find the analogue in first and take it from there, let me know how you get on as this isn't easy for me either.

PS:

Resistance reduces in parallel, and increases in series.

EG 2 x 1000ohm resistors in parallel give a overall resistance of 500Ohms, but if you put them in series you'll get 2000 Ohms. Good luck.

[ian.mich]

This has me stumped. then again, im no EE

Me neither, but I'm trying to do something similar to you, I'm trying to change the HVC on an eZee controller, as it's made for 36v and I'm using a 48v battery.

Here's what I've done so far, I think I'm almost there: First I found the main microcontroller chip, it's a PIC16F73 in my case.

Then lookup the datasheet and find the pinout, here's mine:



Pins 2,3,4 and 5 are of interest here, they are analogue ins.

What I did next was to vary my battery voltage in even steps, and measure the voltage on these pins. If you are lucky, 1 pin will vary evenly with input voltage. Here are my readings, and pin2 on the PIC16F73 was my pin that changed in proportion to battery voltage:

Battery voltage / Pin 2:
40.4v (10s) / 3.657v
32.36v (8s) / 2.923v
24.31v (6s) / 2.196v
16.23v (4s) / 1.468v
8.07v (2s) / 0.731v

Now I already know that the LVC on my controller is 28v and the HVC is 44v, and this equates to the voltage on pin2 being above 2.5v and below 4v.

What I'm doing now is trying to trace back the resistors which are in series with pin2, and I'm going to try and change the resistance so that an input battery voltage of 36v produces 2.5v on pin2 for the LVC and a battery voltage of 53v produces a voltage of pin2.

This should work in theory, but I've never done it before, so don't take my word as gospel.

Try and find the analogue in first and take it from there, let me know how you get on as this isn't easy for me either.

PS:

Resistance reduces in parallel, and increases in series.

EG 2 x 1000ohm resistors in parallel give a overall resistance of 500Ohms, but if you put them in series you'll get 2000 Ohms. Good luck.

i believe it would be (1/1000)+(1/1000)=rt, so .002 ohms.
Thank you for the insight, i think i know what i'm doing with my first day of finished exams
i'll start looking for that pin. So you think that pin 1 on your processor is the LVC? did you just put both +ve and -ve of the voltmeter on the pins?

[HypnoToad]

i believe it would be (1/1000)+(1/1000)=rt, so .002 ohms.
Thank you for the insight, i think i know what i'm doing with my first day of finished exams
i'll start looking for that pin. So you think that pin 1 on your processor is the LVC? did you just put both +ve and -ve of the voltmeter on the pins?

No problem. I think you may have an error in your resistor formula however, I believe it's this for parallel:

1/r1 + 1/r2 = 1/rt

http://www.sengpielaudio.com/calculator-paralresist.htm

So it is 500 ohms in this case.

Pin 1 on my micro controller VPP which I think is the power supply to the chip.
Pin 2 - analogue in 0 turns out to be the pin on the chip which varies with input voltage, after going thru what I image to be a potential divider. I plan to change the resistance of one of the resistors in the potential divider in order to adjust the LVC and HVC.

now in order to measure the voltages, I put my black wire on my DMM to battery ground, and the red wire on pin 2 of my micro controller. You need to be pretty careful not to short the pins on the chip as they are pretty tiny.

You may be able to trace the pins to a nearby component which can make measuring easier.

On my Ezee controller pcb, pin 2 leads to r8, a surface mount resistor so I measure from this instead. That way if I slip with the probe there is less chance or shorting out something.

What micro controller if on your green time unit? It help to find the pin out before measuring. The micro controller is usually the ic with the most amount of pins.

[ian.mich]

Darn, forgot about 1/rt. It's an x8m06, can't find a datasheet anywhere, ill keep looking

[ian.mich]

Couldn't find the sheet, but after much testing, seems that I found a pin that varies depending on voltage. It seems I was right when in my first post, changing the resistor shown below is the way. Now I just need to get the all-clear from Leo and i'm going to do it.

[HypnoToad]

Darn, forgot about 1/rt. It's an x8m06, can't find a datasheet anywhere, ill keep looking

Google x8m06, alldatasheet seems to have some info.

Good to hear you found the magic pin, swapping/adding resistors should do the trick

[ian.mich]

Darn, forgot about 1/rt. It's an x8m06, can't find a datasheet anywhere, ill keep looking

Google x8m06, alldatasheet seems to have some info.

Good to hear you found the magic pin, swapping/adding resistors should do the trick

http://www.alldatasheet.net/view.jsp?Searchword=X8M06
no luck, just a bunch of other parts

[ian.mich]

He sent me the layout of the board
http://www.pdfhost.net/index.php?Action ... 7eb0ed3a6b
The resistor I believed to be the LVC modifier is in fact the correct one. It is RJ15K near the VCC, confirmed by leo

[HypnoToad]

He sent me the layout of the board
http://www.pdfhost.net/index.php?Action ... 7eb0ed3a6b
The resistor I believed to be the LVC modifier is in fact the correct one. It is RJ15K near the VCC, confirmed by leo

Now you know hitch resistor you need to experiment with, google up 'pencil mod' and this will give a quick and dirty way of reducing resisance on a SMD resistor

However, I'm not sure how durable running a pencil mod beyond testing would be; it's probably better to break out the soldering iron once you have your esistance values

[ian.mich]

He sent me the layout of the board
http://www.pdfhost.net/index.php?Action ... 7eb0ed3a6b
The resistor I believed to be the LVC modifier is in fact the correct one. It is RJ15K near the VCC, confirmed by leo

Now you know hitch resistor you need to experiment with, google up 'pencil mod' and this will give a quick and dirty way of reducing resisance on a SMD resistor

However, I'm not sure how durable running a pencil mod beyond testing would be; it's probably better to break out the soldering iron once you have your esistance values

Yeah im probably going to pencil mod until i get the correct LVC for 16s or 20s then test the resistance with my "ohm-meter" (as if that really exists) just to see what the resistance is. Luckily they put a 2nd spot for a resistor in parallel, so it makes this a lot easier to set a specific . . . ohmage? Eventually i'll order SMD resistors on ebay and figure out the correct R value for 12S at 3v, 16s at 3v, 20s at 3v for my customers, and 24s at 3v for myself