Step 5: Power Section construction details

These photos show how the FETs and power diodes are attached to the heat sink.  They must be kept electrically isolated from the heat sink.  The screws are covered with 1/8" heat shrink tubing and the FET and power  The heat sink that I used is re-purposed from an old broken PC power supply.
Really this project is interesting for engineering students and it also intents them to do next level so millions of thanks to author :) (Y)<br>And i'm also doing my e-bike with this instructables i got idea to design my controller with basic functionalities but now i stuck at one point the motor that im using was BLDC three phase with hall elements at stator.I dont know how to design a controller for this application.So pls someone(preferably author of this project) help me to ctrl my motor.Thanks in advance :)
For a sensored BLDC motor controller, you will need to control (at least) 6 FETs (3 phases x 2 current directions). At any one time only 2 of the 6 FETs are active and of the 2 active FETs, one is on and the other is PWM modulated for speed control. I am not an expert on 3-phase motor controller, so I cannot offer much specific advice, but there are many sensored BLDC motor control application notes available that can help you (just try a google search).
Thank you sir :)
<p>This project is awesome.</p><p>I can't see the schematics in good quality... i can't read the values. Can you post it in high resolution or in PDF format.</p><p>Thanks for all.</p>
Done :)
Thank you very much.
Did you have pwm code
<p>Hi, </p><p>Please can you share with us the software part :) ??</p><p>Thanks for all.</p>
<p>Can we smooth out a square wave to reasonable sinewave, (like our grid mains supply) with passive inductor or capacitor? The square wave gives harmonics, tiny stutters and less efficiency. </p>
The FET gate needs to be turned on/off quickly, otherwise more time is spent in the FET's linear/resistive region and thus more heat will be generated.
<p>Yep, figures,... so can a capacitor-resistor be made to slow the FET's output to a less abrupt rising and falling voltage after the FET has switched in its efficient square wave fashion ?? I'm also thinking of audio passive RC filters that can be tuned to smooth out a square wave. I need to buy a scope and experiment ;-)</p>
<p>Most motor controller designs have some parallel capacitance on the output to the motor (my controller has 3x 470uF caps), and the motor itself is a resistive and inductive (but primarily inductive) load, so there is some filtering happening. I would not recommend adding any series resistance, but you might experiment with adding (or subtracting) parallel capacitance and measure the effect on the motor voltage waveforms.</p>
<p>Hello..do we really need a controller for a hub motor ...can we just hook a battery to it <br>and a switch to press on when we need the extra boost when we are tired of pedaling?</p>
As you suggest, for a DC motor it would be possible to just implement a &quot;boost&quot; switch for cruising. You would need a very robust switch because of the high currents involved, but this would be dangerous since high current would be flowing through the switch. A relay would be safer since it offers some isolation and a solid state relay would be more reliable than a mechanical relay, but once you've done all that then you are very close to just implementing a controller ;)
<p>Hi!</p><p>in one model of arduino (arduino Due) it has 2 real analogue output. I am thinking of using these analogue outputs instead of PWM. Do you know any driver circuits working with analogue signals instead of PWM? Because sometimes the noise of a motor controlled by an analogue signal is less than when it is controlled by PWM. </p>
<p>Why the MOSFETs need to be electrically isolated from the heatsink, in the schematic the Drain pins are connected together anyway..</p>
<p>To get better heat transfer</p>
It is safer. Bicycles can vibrate and shake and it may be possible (for example) for the case to accidentally contacts the heat sink.<br>
<p>Will this controller work if use 36volts instead of 48?</p>
This controller will work at either 36V or 48V since it does not do any low-voltage checks on the battery. I just manually check the battery before and after every ride and I my commute is short, so I never over-discharged the battery. However, adding a low-voltage check to the controller would be a good (and recommended) enhancement that would help protect the battery from over-discharging.<br>
<p>I am totally blank on electric motor controller designs and i am looking for a multi-motor controller for my DIY electric bike &amp; scooter. I was told I can use a stock controller with proper voltage and wattage (especially, wattage) to control two brushed motors for either bike or scooter. My goal is to use two low wattage hub motors (front and rear; kinda like all-wheel-drive) to drive an electric bike or scooter. your article gives me a close look into the construction of controller. thank you!!</p>
<p>is it single phase dc motor? can you send me its link. </p>
<p>It is a single phase brushed DC motor. Brushless motors are more reliable in general, but demand a more complex controller.</p>
It is a Crystalyte Sparrow.<br><br>http://www.electric-scooters-info.com/Crystalyte/crystalyte-sparrow-electric-bike-kit-review.html<br>
<p>Good work...</p><p>I would also like to design a speed controller for 48 V/1000 W BLDC motor on a bicycle. I wanted to integrate Cruise control, few cut off functions, and be able to externally display velocity,voltage,rpm,etc. Would a PWM circuit works fine or should i use an Ardrino instead? I am an Electrical Engineering Tech student, but had done very basic microcontroller programming . How could i proceed?</p>
I used the free C compiler that comes with the Atmel AVR Studio software. I have not used Arduino, but I have heard that many functions are easier to implement because they have Arduino library support. You could do all the features that you listed using a simple 8-bit Atmel ATmega8, but you may also want to look at the newer 32-bit Arm-based microcontrollers which really don't cost much more than the old 8-bit controllers and they have more capabilities. I'm sure you will have lots of fun exploring. All the best !!<br><br>Regards,<br>Scott<br>
excellent for a greener world
Hi, can you mind teach me how to choose a suitable motor to drive an e-bike. The weight that the motor can support is 100kg. So, how I am going to choose a motor that can support 100kg of weight? <br>Thanks...
I weigh about 100kg and I use a non-geared hub motor that is rated at 750W. I still need to pedal on hills, but overall I find 750W is adequate. I suppose the answer depends on a) how much you want to pedal and b) how flat or hilly is the terrain in your area.<br>
I was working on E-bike project using a 0.5HP (360W), 48V brushed motor (PMDC), so the current here will be around 8A or 16A while starting, with this circuit, will I be able to achieve speed control without burning the motor? If no, what will be the changes, especially in the motor driver part, which IC should I use.
To protect the motor from over-current, the controller needs to have a current limiter. I had planned to include this in the firmware, but never got around to it. The current limiter firmware would need to periodically read the shunt voltage and calculate the average current, and it this exceeds the maximum allowed current then the PWM would need to be shut down.
I am looking oout for a complete design and source code to controll a BLDC 250W motor for an e cycle project, battery could be either Lead Acid or Li-Ion of 24V with trottle control and Break cut off. Can any one help me. I am ready to pay professional charges for this project. My mail id is myshanks(at)gmail.com
Which kind battery did you used. Ordinary lead acid battery or NMH or another type battery. And also I will ask the Power of the battery howmany Amper-Hour? And you said 10 miles trip every day is your way stright? You made agood job thanks for sharing this project
I have had a few e-bikes which have used either &quot;deep-cycle&quot; lead-acid batteries or LiFePO4 Lithium Ion batteries. The deep-cycle lead-acid batteries are OK, but they are heavy and they don't take as many charging cycles as LiFePO4 Lithium Ion. I have found that a 10AH battery is adequate for my10 mile commute which is mostly-flat with a few small hills. I weigh about 200 lbs (about 90.5 kgs). I peddle while I ride, but I think the motor does more work than I do :)<br>
Nice to see a design for this. How much current does the board itself take?
The prototype board is hand wired using 12AWG wire for the power sections so it should be able to handle 50 Amps or so. A printed circuit version would require using heavy (3oz) copper clad circuit board material and/or beefing up the traces by soldering wire in parallel with the high-current traces.<br><br>For handling really high currents in a DC motor controller, you should check out this instructable by Paul Holmes:<br><br>http://www.instructables.com/id/Homemade-100-HP-Motor-Controller-for-an-Electric-C<br>
Sorry, I phrased my question badly. What I was asking about was the actual current used by the controller board electronics to run, not the current it is capable of controlling. Thanks.
I have not measured it, but it is small compared to the current supplied to the motor. The primary current consumers would be the 7805 regulator, the ATMega8, and the FET drivers. The ATMega8 data sheet states 15 mA max Icc. I do not have data handy for the 7805 or FET driver current consumption.<br>
Thanks for this. I was just wondering if it was worth using a linear voltage regulator chip in the 78 series, but I see they are usually max. input of 35-40v so your dc-dc convertor looks like a more appropriate design.
This motor controller uses both 12V (for the FET gate drive) and 5V (for the ATMega8, etc.). I used a DC-DC converter (from my other instructable) to generate the 12V (from the 48V battery) and then I used the 7805 to generate the 5V (from the 12V input).
just so so.
so this is not yet an instructable, but a concept yet on pwm motor controller! good design idea though!
Why do they need to be electrically isolated?
Because the case of the diode is electrically connected to its cathode and the case of the FET is electrically connected to its drain. If you don't isolate these from the electrically conducting heat sink, then you've just made a short from motor+ to motor- :)<br>
One could use 2 separate heat sinks if one does not find the isolators.
Typo on the notes on image, bottom right: block instead of black
Thanks, I have fixed it .. :)
You rode the bike for already 2 months, but say the software is not available!<br><br>Forgive me, but why then would anybody but a complete expert build this?
The software is not available because I have only coded the basic PWM function. Other important functions (e.g. the battery under-voltage check and the over-current check) are not coded yet. So it's good enough for me since I know the limitations, but it is not good enough to post.<br><br>

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