Big voltage H-Bridge DC motor control

technoob

I have seached the entire internet and have found countless H-bridge type motor controlers.· some with logic·, i2c and radio control interfaces.·· Some with just a throttle Pot.
····· Every one of them wants between 80 and 150+ dollars.· I want to build my own.·· I have found alot of shematics for low v and low amp devices but I cant find designs and parts lists for the big Voltage stuff.·
I need a schematic and parts list for a simple motor H Bridge dc motor controller.·

48 volts
30 amps
60 amp peak.

big heat sink



If anyone knows of a web site or whatnot
Id appreciate a shove in the right direction.···

Im kinda new to this stuff so be gentle..

thanks
Randy C

SRLM

Can't you just use relays instead of transistors for the motor power part? Then, you can just select four relays of the size you need.

technoob

I tried using a relay and experienced an unplesant smell and a slight blinding affect when i hit the switch.· Since the motor isnt running its start up load is significant.· It acts like a short circuit until it gets spinning and the load drops.·

R,I,P. 24v relay



rc

Geekgirl

That initial inrush current is the killer.·

What you may want to look into is using IGBTs as switches for those load demands, as opposed to mosfets, though mosfets could still be an option if you parallel enough of them.

Big solid state tesla coils use H bridges designed to handle mega loads and studying up on the coiler sites would get you familliar with H bridge design·of that power level.

The H bridge would allow for speed as well as direction control, while the mechanical contact H bridge wouldn't allow for speed control.



If all you need is on/off and·direction control, you could still implement it with mechanical contacts, but think "accross the line starter" not relay. Therer are starters to control motors any motor size, they·need 120vac to operate them, so you'd need to use an SSR as the link between your stamp and the control windings of the starters. They also have options for control contacts that you can wire to prevent one pair from pulling in untill the other pair has fully released.

remmi870

what kind of motor are you running? ive had experience with large motor controllers, 3 phase, ac 50hp motors, 70A+ at 480 v, your best bet is to use two IGBT to form a h bridge, then you can wire the IGBT to "ramp up" using pwm to controll the current and voltage during startup to save your motor, the only other option is to use large solenoids, like car starters use, wired up in a similar H bridge fashion, but there are a finite amount of cycles you can use, not to mention if you use IGBT you may be able to use dynamic braking depending on your IGBTs and circuitry.

Propability

·Just a thought. Have never done it but maybe a solid state relay for controlling the current (PWM) and just a relay for direction.

erco

I love relays for small robots. When I built my electric bike (http://www.youtube.com/watch?v=eYh2JaHsdak) I first tried an automotive lighting relay rated at 20 amps for simple on/off control. On the bench it worked fine, but on its very first road test, the inductive motor load welded the relay contacts together for a very exciting runaway full-throttle acceleration. Fortunately I had a 70-amp master cutoff switch to kill the power so I'm still here to say "don't use a relay".

Thus I·came to·appreciate the $20 Chinese controllers·at http://tncscooters.com/partsdb.php?type=ES·. They come in 12, 24, 36 and 48-volt versions with overload protection. Only a couple have reverse, so I would count on using heavy duty relays for reversing that will only switch when no current is flowing.

These would make great and affordable robot motor controllers. All that remains is figuring out how to get the stamp to output proper control signals. The stock hand throttle uses a Hall-effect sensor to generate the signal.

Great geared bike motors available on that website for ~$55 that would be useful in a robot.·Have a peek at all the other parts available, and also check on ebay for electric scooter parts.

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·"If you build it, they will come."

Post Edited (erco) : 2/12/2009 10:57:48 PM GMT

technoob

I FOUND IT!!· Motor controler that is....

Check out·my video on you tube. http://www.youtube.com/watch?v=MShHCcN7Ul8&feature=channel_page

The Golf cart motor controler cost me 50 bucks used.· No bad for the stats.·· Look up the data on

http://curtisinst.com/index.cfm?fuseaction=cProducts.dspProductCategory&catID=11

Its the 1204 unit.···· check out your local golf cart dealer.··· Alot of people upgrade the motors and batterys systems so the cart guy pulls these contorllers out and has them laying

around.·

This is phase one.

Phase two is to get this rig mounted on a stable platform and get the motor geared down a bit and add a braking system so I can simulate load.

Once that is done I go crazy with the BS2p40 and a bunch of Dallas One Wire chips to build a better battery management system.· Ill post another video once I have the rig mounted and and currrent varible braking systme installed.·· I plan to have a BS2 manage the brake system, Motor RPM and On OFF for the motor.·· That way I can set up complete simulations to run for extended durations for complete battery cycle testing.···· OOO this is cool!!!!

Later guys and gals.·· You peeps are awsome!!!

Technoob!!!!

remmi870

what do you plan on doing with this setup?

technoob

Why you ask?

·'..........................[noparse][[/noparse] Inster mad laughter here]............................

Well

China sends us these cheesy battery managments systems and really random Motor Control units ·to go with our LiFePO4 batteries.·· They are really sad and inconsistant.·· My plan is to utilize this load mock up to begin designing an intergrated Motor control and Battery management system using the BS2p40..· and lots of sensors and lots of ... stuff..... (Dallas One wire and I2C stuff actually)


Next on my immedate agenda is to mount the motor and create a variable loading device for it.··· Im thinking of using a hydrolic automotive brake caliper and rotor.··· the reason for the heavy duty equip is this.···· I plan to automate the load center with a BS2 so the system can run atonomously for the duration of a battery discharge cycle.· I dont want to sit and watch it run for 20 hours.· I will use a liniar actuator to affect the brake master cylinder· ( brake pedal )· It will cycle as per program to simulate load through out the discharge cycle.··· Ill calculate shaft·RPM to come up with a simulated MPH for my application wheel diameter.·· A digital throttle contorl for the motor will vary the load input voltage to compensate for the kenetic drag applied by the brake to maintian MPH (therby creating increased current draw [noparse][[/noparse]load]).· I hope to gather an array of critical data and pitch it out to my pc via rs232 for analysis in excell..· groovy graphs and what not...

the questions are.:··· How does the BMS and MC deal with varied loads and what is the most efficient configuration?·· What is required to defend the batteries from excessive disharge rates and heat?· (obviously the answer to these questions will inevitablly breed 50 more questions and so forth.·· think "Star Trek Tribbles")

YOU ASKED!..·· lol

As I navigate my way through this maze of technical madness I hope to create a marketable bms for any application by designing a framwork with the BS2 family of products.· the future is electric and must have batteries.·· Battery life is directly associated with Battery Management Systems.·

Im a noob.·· I hope this works.··