Sunday, February 22, 2009

Drive cutout issues

I have Gizmo #31. This Gizmo has a D&D SepEx motor and Sevcon PowerPak controller.

Through trouble shooting intermittent drive cutout issues over the past couple of years I believe I have an understand of how the NORM circuit works on this vehicle. This vehicle also has circuitry installed to enable constant regen when the brake light comes on. The NORM circuit affects this too.

My NORM circuit has 5 wires attached to it. The pink wire is attached to the switched +12V line of the DC-DC converter. The White wire is connected to battery pack negative. The blue wire is connected to pin 4 on the controller connector B and is called the FS1 line according to the controller manual. In conjunction with the NORM circuit is a hall effect device in the right hand control handle to provide feedback based on throttle trigger position. One wire is labeled "-" (black wire on my rig) and is connected to the white wire on the NORM circuit (battery pack negative). On the opposite side of the hall effect device is another wire labeled "+" (pink wire on my rig). This wire is connected to the yellow wire on the NORM circuit. The NORM circuit has a voltage regulator which puts out a +5v on this yellow wire. In the center of the hall effect device, between the + and - wires, is a third wire (orange wire on my rig) which connects to pin 10 on controller connector B. This line is an analogue input from 0-5V and is what the controller reads as torque request. In addition to connecting to pin 10 on the controller the center wire from the hall effect device also connects to the orange wire on the NORM circuit. This is necessary because the NORM circuit needs to know when throttle input is requested so it can control the state of the FS1 line. The schematic is below:On power-up the NORM circuit must have FS1 in an open state so that the Controller will boot up without giving a sequence fault. If FS1 is closed (shorted to battery pack negative) then the controller will sequence fault as a safety precaution. When the throttle trigger is pulled it sends a portion of the 5v coming from the NORM circuit out to pin 10 on the controller. On my rig this ranges from 0.82-4.24v as seen by the controller. When the controller sees a voltage greater than its lower threshold it knows that torque is requested but it won't do anything if FS1 is open. This is why the NORM Circuit must have a connection to the output of the hall effect device. The NORM Circuit monitors the voltage from the hall effect device and when a voltage greater than the lower threshold is seen the NORM circuit closes the FS1 line and drive will commence. Provided of course a direction is selected and no other fault conditions exist. When the throttle trigger is released the NORM circuit opens FS1. On my rig regen is enabled by the brake light. Regen, however, is disabled if FS1 is closed. This is why FS1 must be open when no throttle input is selected. If I didn't have regen FS1 could remain closed after the controller boots up and I wouldn't notice.

I don't know what kind of mechanism is used to close FS1 but it seems to be what has caused nearly all of my drive cutout problems. I have had the following drive related issues:

1) No drive on power-up because FS1 was closed, this caused a controller sequence fault.

2) No drive after power-up because FS1 remained open even when drive was requested. If I held the throttle in for 5 seconds-5 minutes sometimes drive would start to work. This usually happened if the sun had been shining on the vehicle for a while but eventually it didn't matter.

3) Similar to #2 but would happen while driving but only if the throttle was released.

4) Drive would cut out while moving and throttle still pressed because FS1 would open.

5) Regen would start to work then cut out or just wouldn't work at all.

6) Regen would pulse on and off, usually at speeds below 25 or so but sometimes at all speeds.

I believe that all of these issues in my case have to do with the NORM circuit not properly handling the state of FS1. To deal with these issues I installed a SPDT switch in the FS2 line as shown in the schematic. The common side of the switch is connected to the FS1 line (pin 4 on controller connector B). One side of the switch is connected to the blue wire on the NORM circuit. The other side of the switch is connected to battery pack negative. I chose an on-off-on style of switch so I have some options. For normal operation the switch is set to connect the blue wire to FS1. If on power-up the controller gives a sequence fault (2 blinks) I switch the switch to the off position momentarily to clear the sequence fault then back to normal operation. If the NORM circuit is just not closing FS1 I switch the switch to short FS1 to battery pack negative and I can then drive. This is how I deal with items 1-4 above.

To deal with items 5 & 6 regen I switch the switch to the off position and regen works just great. No pulsing and it never cuts out until the speed is too slow, of course.

The problem with this is that the switch has to be switched back to one of the on positions for drive to work. This is a bit of a hassle but it sure beats being stranded.

Right now Ron Anderson of Black Sheep Technology is working on a replacement unit. We hope to integrate regen into the unit too so that others can easily add regen if they have the same controller setup as I do.

Hopefully this helps. Feel free to contact me if you have any questions.