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Posted: **Mon Jan 30, 2017 1:16 am**

Can you connect a meter in series with the heater and measure the current?

Posted: **Mon Jan 30, 2017 1:23 am**

So like

3) DIAHD silkscreen on pad #6 should be DIAHG
4) add a note describing UR (R8) and UA (R15) low pass filter / slew rate limiter
5) add a note explaining different C2 and C9 values

Poking @ about cutting the heater wire and adding A-meter into the cut.

Posted: **Mon Jan 30, 2017 1:30 am**

The GND pad is a large heat sink. How confident are we that we got a good solder flow on the leads? If we have 10A of current running through a 0.1ohm resistance, that would generate (10^2)0.1ohm = 10 watts.

What is the voltage on the gate? Measured referenced to the GND side of the MOSFET. Perhaps there is a voltage drop on the GND side of the MOSFET which is causing the gate voltage to be not fully driven. Perhaps it's in the transient instead of saturated state.

Posted: **Mon Jan 30, 2017 1:34 am**

Looking at the above picture, you need more solder on the MOSFET leads. The other leads probably need more solder as well, but it's less noticeable as you have much less current flow.

Posted: **Mon Jan 30, 2017 7:14 am**

I'd say, for it to be a filter, the resistor should be before the capacitor? Unless the STM chip is an output, rather than an input.

Sent from my XT1058 using Tapatalk

Posted: **Mon Jan 30, 2017 7:34 am**

blind me, but where do I see your CJ125 code?

Posted: **Mon Jan 30, 2017 7:47 am**

kb1gtt wrote:I think the question is for UR (R8) and UA (R15). I forget why those had the 1k resistors. I'm reasonably sure it's a low pass filter / slew rate limiter. I forget where I got those values from. I'm sure it was off a datasheet or example some where, but I forget where.

RC filter usually converts PWM signal to analog. But out from cj125 already analog (not pwm)

Posted: **Mon Jan 30, 2017 11:41 am**

We can change those to 0R's and see how it works. I think it was a generic anti aliasing filter.

Posted: **Mon Jan 30, 2017 12:21 pm**

Btw, don't we need a voltage divider (don't remember the voltage level from cj125, but as far as I remember it works from 5v?)

Posted: **Mon Jan 30, 2017 1:00 pm**

R12 is connected incorrectly.

Posted: **Mon Jan 30, 2017 4:29 pm**

Rhinoman wrote:R12 is connected incorrectly.

correct observation

Posted: **Tue Jan 31, 2017 1:49 am**

3) DIAHD silkscreen on pad #6 should be DIAHG
4) add a note describing UR (R8) and UA (R15) low pass filter / slew rate limiter
5) add a note explaining different C2 and C9 values
6) R12 is not routed right

Posted: **Wed Feb 01, 2017 1:02 am**

R12 moved, recalibrated, solder added

Same issues: hot mosfet. Dmm shows 0a on heater wire. Ideas?

Posted: **Wed Feb 01, 2017 1:26 am**

I did as told ...
the result is zero ...
It gets very hot mosfet ...
maybe mosfet burned out ???

Posted: **Wed Feb 01, 2017 4:27 am**

What is the voltage on MOSFET pin 1?, I guess same for the other pins.

There are many protections on this MOSFET, burt out is not likely. More likely it's oscillating or not driven fully, or something like that. Seems odd it's getting hot but 0A. Where are the watts coming from? Could the MOSFET be switching on and off really fast, at such a high frequency that the DMM doesn't see it? Can you put a scope on the gate, or source?

Posted: **Wed Feb 01, 2017 7:09 am**

could it be that the DMM is broken?

Posted: **Wed Feb 01, 2017 10:50 am**

Did you check the DMM with another DMM to verify the internal fuse was OK? Typically the 10A doesn't have a fuse, so it's probably OK. Also can you connect it to another DMM in the diode setting. That should measure like 10mA. It would verify the meter display is OK.

However if that was open circuit, then it still doesn't explain why it's getting hot. Could you replace the MOSFET? I would not do that yet, but I wonder if it is a possibility.

Posted: **Wed Feb 01, 2017 12:20 pm**

kb1gtt wrote:Could you replace the MOSFET? I would not do that yet

I have more of these MOSFETs obviously. Source code says we are running PWM at 500Hz.

Posted: **Wed Feb 01, 2017 12:32 pm**

what does the scope shows on the gate of Q1? may be the 3.3V is insufficient to drive it? Is Atomic-dm using the same 3.3v level chips to drive it?

Posted: **Wed Feb 01, 2017 12:33 pm**

@ do you have any of http://www.ebay.com/itm/112035273840 boards by any chance? I could ask @ if he would share his STM32F103 firmware prototype with you if you are interested.

Posted: **Wed Feb 01, 2017 12:35 pm**

puff wrote:Is Atomic-dm using the same 3.3v level chips to drive it?

Yes, @ is using same STM32F103 minimal board as we do. We are also using his firmware. The only difference is that we are using our board and our mosfet.

@ also has a PCB for our board so there is a chance he will solder it one day.

Posted: **Wed Feb 01, 2017 12:52 pm**

russian wrote:@ do you have any of http://www.ebay.com/itm/112035273840 boards by any chance? I could ask @ if he would share his STM32F103 firmware prototype with you if you are interested.

I don't but I could source one. My Oshmon PCBs have been despatched but I haven't received any notice that my CJ125s are on the way.

Posted: **Wed Feb 01, 2017 5:05 pm**

Does it still get hot if the PWM is changed to 0% AKA is this a copper bridge or some kind of physical problem. Then does it got hot if PWM is 100%. This will tell is if it's an switching issue, or a DC issue.

Posted: **Wed Feb 01, 2017 6:14 pm**

Or Q1 was chosen incorrectly? Or a faulty board?

I wonder why the guys who have a scope don't use it?

I wonder, whats' the role of DIAHG pin on CJ125 - am I right that it is pulling it high (closing Q1) when something goes wrong, overriding PWM from STM chip? Could it be that CJ is driving it up, but doesn't have enough power, so that Q1 is semi-closed (but then again, it doesn't explain 0A?)

What happens when you apply PWM to power up an inductive load? (don't we need a diode?)

Don't seen any resistance on the Q1's gate (which is present in other similar schemes)

Posted: **Wed Feb 01, 2017 6:16 pm**

maybe pwm signal very fast for this mosfet.

if you have more one mosfet, i recommend change mosfet. if it not help - do pwm more slower

Posted: **Wed Feb 01, 2017 6:33 pm**

Have you used a clamping diode across the heater contacts?
Do you have a resistor between the mosfet gate and STM?

Posted: **Wed Feb 01, 2017 6:42 pm**

We are wasting time. We need one of the EE guys to have the setup in front of him.

Abricos to ship stuff to kb1gtt, or atomic-tm to assembled his board, or Rhinoman to assrmbled his board.

Posted: **Thu Feb 02, 2017 1:30 am**

Hmmm, looks like 1kHz is the absolute maximum for this chip, and if you are at the maximum delays for some reason, then 333Hz is the absolute maximum. Even at 500Hz, your spending allot of time in the transition part of the pulse. So it might be to fast of a switching frequency. Also what is the duty? Is this 50% duty? You probably can't be very far from 50% at 500Hz. Might be worth trying something like 100Hz or below.

Also also, is the port configured correctly? AKA not drive high, then float. Is it driving both high and low? If it's driving hi and low, is it doing it with the weak pull ups, or the strong transistors?

Posted: **Thu Feb 02, 2017 1:48 am**

I've just compiled hopefully a 125Hz version of that firmware, @ will probably try tomorrow.

Code: Select all

pwm.c
	TIM_Time_user.TIM_Period=255;  // russian: 1023 replaced with 255               
main.c 
        float maxU = 255;// russian: 1023 replaced with 255

Posted: **Sat Feb 04, 2017 2:38 am**

New information:

@ has a resistor divider on UR analog line with two 100K resistors. On our board we can remove C2 and install 1K resistor.

Also apparently PWM is much slower than we though: original firmware is just 11Hz, modified firmware is 44Hz. Could this be causing any problems? Should we play with 11Hz or 44Hz or 88Hz or 172Hz?

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