Friday, September 21, 2007

An E-mail from Azure Dynamics about the DMOC445

I recently sent off an e-mail to Azure Dynamics, the maker of the DMOC445 AC motor controller in the 914 kit. I asked how I could tap into the motor encoder signals to create an RPM signal for the tachometer on the dashboard. It turns out that the DMOC controller already has a PWM (Pulse Width Modulated) output that can be used for this. There are also some LED signals that display system status without having to use the serial port.

I would like to express my sincere appreciation for all the tech support that Azure Dynamics has provided. Beth Silverman, the support person, has been very quick to respond with whatever information she can provide from the controller designers. Here's the e-mail:

Hi Tim, inserted below in blue are our answers to your questions. I understand you've been communicating with Randy Pollack; is it ok if I pass your questions on to him along with our answers?
Beth Silverman

From: Tim Kutscha []
Sent: Monday, September 17, 2007 8:34 PM
To: Beth Silverman
Subject: Re: tapping into the encoder signals to drive the RPM gauge

Hi Beth,

I hope you had a good two days off last week. Thanks for the info on the SPEEDO_BUF output on the controller. Since this wasn't listed in the Pedal_Controlled_DMOC445_User_Manual_v3.pdf file, I didn't think it was active. From your e-mail, it sounds like the SPEEDO_BUF output is active on my pedal-controller DMOC.
Feature is active on both pedal and CAN controlled

From one document it says the signal is 12V open-emitter. I'm guessing its a PWM (pulse width modulated signal) that pulls an external resistor up to 12V through a transistor. Is this true?
SPEEDO_BUF is push-pull 12V, and it is a frequency modulated signal.

Is the SOC_BUF signal also active on my DMOC445? What is the format of its output? PWM? Does it get its state from the battery voltage or does it require the amp-hour counter to be attached?
Not active

Do the amp-hour counter input/outputs work? If so, do you sell a device that I can connect to them?
Not active; we do not sell amp-hr meters.

Do the BRAKE_PEDAL,BRAKE_LO inputs work? If so, what is the proper potentiometer to attach to them?
Not used

Is there any customer useful behavior on the ANAIN3/LED_OVERTEMP, ANAIN2/LED_MALFN, NONISO_ADIO1, NONISO_ADIO2, ANAIN1 or ANAIN0 signals?

LEDs are 3.3V (unfused outputs). If an LED is connected to it, a current limiting resistor is needed.

LED0: Fault-Signal on pin 34:
- (________): off = no fault
- (_______x): one short blip = motor overheating
- (_____x_x): two short blips = controller overheating
- (___x_x_x): three short blips = motor and controller overheating
- (_x_x_x_x): continous blink = not implemented
- (xxxxxxxx): continous on = powerstage fault
LED1: Ready-Signal on pin 11:
- (________): off = controller disabled (pin 8 = low; or pin 8 = high and pin 30 = high)
- (_______x): one short blip = controller enabled, but pre-charging
- (_____x_x): two short blips = controller enabled & pre-charged, but interlocked
(for example due to gear-selector being in forward at powerup)
- (___x_x_x): three short blips = N/A
- (_x_x_x_x): continous blink = relay closed, but power-stage in fault state
- (xxxxxxxx): continous on = ready (relay closed, power-stage disabled or enabled)

The car is basically running at this point and I'm try to activate as many gauges as I can. Thanks for all your time on this.
Have a great week!


----- Original Message ----
From: Beth Silverman
To: Tim Kutscha
Sent: Monday, September 17, 2007 10:26:05 AM
Subject: RE: tapping into the encoder signals to drive the RPM gauge

Hi Tim, sorry, I was out Thurs and Fri. Are you already using the DMOC output signal -- it can be adjusted with the parameter called EE1SpeedoDiv ?? It doesn't work with all speedos/tachs, but we have had luck with the Siemens VDO "Cockpit" series, 85mm. Please see
Beth Silverman

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