# What features would you like to see in a budget controller?



## Nate (Jul 10, 2008)

*This is just my opinion,*

*No low voltage cutout. Allow the controller to operate on all voltages up to the maximum to so people can upgrade the battery pack without buying a new controller every time.*
*Solenoid control is not a bad idea for safety reasons if this feature is cost effective.*


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## lazzer408 (May 18, 2008)

Nate said:


> *Solenoid control is not a bad idea for safety reasons if this feature is cost effective.*


It's not that expencive. I have a circuit I came up with that drives a small relay (precharge) and also drives the main contactor. It has a +12 input (key on) and a momentary +12 input (start) and once activated, by the start signal, it will close the small relay for 3 seconds before activating the main contactor. The small relay will connect a resistor across the main contactor to pre-charge the controller's capasitors before the main contactor closes. This allows the vehicle to maintain the familiarity of having to be 'started' and helps prevent arking of the main contactor contacts and is easier on the controller's capacitors. If you use the vehicle's signal wire to the starter, the clutch/neutral interlock will still function. I thought this was a nice saftey feature which is why I designed it. In comparison, Curtis recomends a resistor permently installed across the main contacts. I don't care for that.
This circuit is a seperate feature of the controller and is isolated from the traction pack. It's just as easy to build it in a seperate box and would be the end users choice if they needed it or not.

What do you guys prefer for the throttle input? 0-5v or 0-5k?

I plan on the following to be user adjustable.
-Throttle ramp
-Throttle trim (zero adjust)
-Current limit (with 2-step external switch for economy/performance)
-Frequency (adjust for lowest acceptable frequency. 10k~20khz)
-Precharge delay time (if implemented)


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## Nate (Jul 10, 2008)

*Could the contactor circuit sense a problem with the controller and stay open in the event the controller was in a "failed ON" mode? Switching devices typically burn up but it is possible for them to fail ON.*

*0-5K for the throttle, my reasoning is another rare but possible incident. If your throttle wires happen to short together for any reason the controller gets an OFF signal. If the wires break the controller can have a "throttle high" cut-off.*
*If the throttle is 5k-0 and a wire breaks it would give an OFF signal, this is good but if you short the throttle wires you send the controller a FULL ON signal. Shorting throttle wires together is rare but it could happen.*

*As you can see I have done some thinking on this subject, thanks for listening. *


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## lazzer408 (May 18, 2008)

Nate said:


> *Could the contactor circuit sense a problem with the controller and stay open in the event the controller was in a "failed ON" mode? Switching devices typically burn up but it is possible for them to fail ON.*
> 
> *0-5K for the throttle, my reasoning is another rare but possible incident. If your throttle wires happen to short together for any reason the controller gets an OFF signal. If the wires break the controller can have a "throttle high" cut-off.*
> *If the throttle is 5k-0 and a wire breaks it would give an OFF signal, this is good but if you short the throttle wires you send the controller a FULL ON signal. Shorting throttle wires together is rare but it could happen.*
> ...


Being a budget controller it's up to the user to hit his disconnect in the event of an in-use failure. It might not be too hard to add some form of shorted-mosfet pre-detection into the precharge circuit. It would not enable the main contactor if the mosfets are shorted. As far as the throttle protection, yes it will have open/short detection.

I'm trying to stay away from building 10s of sub-circuits to detect every imaginable failure. If I do that I'll wind up using a microcontroller based front end to handle it all. It's hard to build if/and/nor/or/then/not in analog circuits and stay afordable.


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## Nate (Jul 10, 2008)

*You are correct, the key word here is "budget" to many systems will raise the cost.*

*I would like to hear from some other folks on what they want also. *


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## joseph3354 (Apr 2, 2008)

i know i am not half as smart as you two appear to be,and i know next to nothing about controllers.i would think that most of us in the "budget arena" would like to have a controller that if failure occurs it would be in an "off" status.i think the contactor could be activated outside the of the controller. monkey proof for people like me( easy to install! ).


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## lazzer408 (May 18, 2008)

joseph3354 said:


> i know i am not half as smart as you two appear to be,and i know next to nothing about controllers.i would think that most of us in the "budget arena" would like to have a controller that if failure occurs it would be in an "off" status.i think the contactor could be activated outside the of the controller. monkey proof for people like me( easy to install! ).


Unfortunately it's hard to 'runaway proof' a DC controller. The AC ones will just blow up and that's it. The DC controllers are usually low-side switched and mosfets CAN and DO blow in a shorted state. Same goes for IGBTs. It would be up to the main contactor, fuse, or manual disconnect to break the current flow. A controller usually blows like this... A single mosfet will pop. The weakest link. When it blows it's likely the gate pin will see the pack voltage across it at some point. That spike hits the gates of the remaining mosfets and blows them all. It also blows the gate driver(s). This is called a cascade failure when the failure of one device causes the failure of another, and another. To help prevent a cascade, I used a zener diode is in parallel with the gate signal -before- the gate resistors. If the zener can hold it, this will cause the gate resistor, of the blown mosfet, to burn up before it takes out the zener and the rest of the gates. It's cheap and might work 50% of the time. If the zener does it's job and the blown mosfet's gate resistor fried, the controller will still function but is down a mosfet. More current will have to flow through the remaining mosfets until another fails. I can't add 32 channels of detection for a 32 mosfet power side.  An easy solution would be a circuit to monitor the state of the mosfets in relation to the gate pulse. If the pulse is 0 and the mosfets are still conducting, the circuit can signal the main contactor to open. I will admit it's MUCH easier to do all this monitoring with a microcontroller. The problem is that all the programers I know think their some sort of code-god and want $1000s to write the code.

If you know microcontrollers and want to work with me to design a system, feel free. (pun intended)

The power-side is already developed. This includes the bus, driver, freewheel diodes, capacitors, and heatsinking. It's only the front end that needs completion.


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## hyper24 (Jun 13, 2008)

Ive done a bit of work with AVR micros.
Ive created a GPS speed limiter, which compares your GPS co-ords to a set list to figure out what street your in. It then gets the speed limit from that list aswell and compares it to your speed from the GPS module.
When you break the limit, it sets off relays which cuts your injectors and brings them back online once you come under the speed limit.

Anyways my point being I THINK im capable to write code for a controller.

Eg. Taking an input signal (throttle) and turning it into a PWM signal to drive something would be few lines of code very quick and simple (infact already done it playing around when I was bored)
Then amp up that pwm signal so it can switch this
http://theelectrostore.com/shopsite_sc/store/html/cm600ha-24h-cm600ha24h-powerex-igbt.html
and hey presto instant cheap controller for $90 bucks

If anyone wants to maybe work together in making an affordable controller?

Maybe we should get some like minds together and start a group project?


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## ngrimm (Oct 19, 2007)

To avoid another debate between micro controller or not it would be best to start a separate thread for a micro controller project. Any micro guys feel like getting something like that started in parallel with this thread?


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## Deekman (Jun 29, 2008)

lazzer408 said:


> I'd like to get some opinions on what features a "budget" controller should have as a minimum requirement....


World-class support. I'm talkin' phone, email, forum, you name it.

This is what made the MegaSquirt project so successful, and it's why they're on their 3rd rev of hardware, umpteenth rev of software and a several thousand strong user base.

Phone support comes in the form of "the guy down the street" with a controller. Email comes in the form of a listsrv, hopefully tied into the forum.

-Deek


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## lazzer408 (May 18, 2008)

Deekman said:


> World-class support. I'm talkin' phone, email, forum, you name it.
> 
> This is what made the MegaSquirt project so successful, and it's why they're on their 3rd rev of hardware, umpteenth rev of software and a several thousand strong user base.
> 
> ...


The support will be forum based. In a forum, "the guy next door" could be on the other side of the world and still be able to help. It's also easy for me to keep track of common issues that might come up.

The whole reason I started the project is because of the lack of higher voltage controllers out there. The 1231 seems to be the only practical option but it's a disposable controller. My design is very service friendly. Every piece, part, and component used in it's construction will be available for purchase. Nothing will be potted unless it's a mechanical requirement. I don't need to "seal the secret". There's no secrets to a DC motor controller.


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