Boxer's PF Electric System Upgrades

[Boxerlego]

Hi, I'm going to be posting all my current electrical modifications for the PF system here and present everything like a guide manual and provide schematic, data sheets, and a parts list. I've been doing a lot of research on electronics lately and been making great progress on it all and decide to start posting what is going on here along with my successes and failures at developing this. I've been contemplatingseveral ideas as how to build this and will be going to demonstrate how to do several things such as convert the IR communication link to 433MHz RF and transmit a possible total of 4 channels out of one antenna and much more. This topic is not only about building off the existing Lego PF electric system, It will contain a basic understanding about the electrical components and look at all the different ideas that can be implemented as to how everything all works together from everything between the batteries to the motors to the controls. One of my main goals here is to up the scale at which models can be built and powered effectively by one or two motors.

One of my longest going disputes is determining a proper battery pack to power my motors. From the very beginning my original idea was to have a 18v battery pack powering a 18v motor. However, awhile back I showed how to upgrade the XL motor with a motor that functions on voltages ranging from 8v up to 16v, so now I'm deciding between either using 12v or 15v battery pack to power the motor. Choosing a battery can be expensive and understanding the battery's voltage range is very critical for the circuit to work properly. There is a bunch of choices here as to what the battery powering the motors should be. I've been thinking on either using a Li-po battery or Li-ion or just continuing on using AA batteries.

The next part of the circuit that is between the motor and the battery is the H bridge motor driver. This is the most critical aspect of the circuit as towards allowing the battery current to the motor and that current is dependent on several factors such as input voltage and temperature. There are several types of transistor out there and it is recommended to have a proper transistor in respect to the device you want to power. By looking at the data sheet it shows that the motor at maximum efficiency current 0.71a and the stall current 5.56a at 12v so here it can be establish that the transistor should be able to handle 10a if two of these motors were to stall simultaneously. The transistor I am using here are know as MOSFETs and the part number on the transistor is IRF540 and the the other one is IRF9540. That is my first H bridge I put together and there is definitely a range of improvements that can be done here.

Now in order to power the H bridge to dive the motor is done by the 9v IR receiver motor connection. There are several ways I've gone about powering the 9v PF receiver from a higher voltage source such as 15v. In the picture below I use a voltage divider which is able to drop the voltage down to a usable voltage supply for the 9v receiver and the amount of current is drastically reduced to the 9v receiver, you will not be able to drive a micro motor with it but you will be able to power the H bridge, One of the main advantage here is using the high 9 volt supply out of the 9v receiver because the transistor is primarily a voltage driven device and that means more current for the motor.

The main part of the upgrade is converting the IR signal to a RF signal. The remote control part of the modification is very easy and does not require much to do, I am almost done with this part. In the pictures below shows the only modification I made so far for the antenna. The benefits here is have a strong base for the antenna to collapse on. It was tricky process to get the antenna screw in that 3mm hole I made, I had to take out the battery metal connection tab on the controller and pass the screw through the battery holder opening in order to insert the screw in there.

Now for the main part in converting the IR signal to a RF signal on the receiver end. While the RF transmitter can handle voltages up to 12v the RF receiver must require a smooth constant voltage around at 3v which can be tricky to do if your using a total supply voltage around 15v, 12v, or even 9v. Instead of using a voltage divider to drop the voltage down to 3v for the RF receiver, I'm going to use a voltage regulator and the reason behind this is the battery voltage will drop when the motors begin to rotate and that will cause a drop in battery supply voltage and the voltage divider will fluctuate in response of this. A voltage regulator will hold a steady supply voltage to the receiver so no matter what the demand voltage is on the battery you wont lose connection with the RF receiver. However, one of the big disadvantages about the voltage regulators is that it converts a lot that energy to heat especially when it is working off a large voltage supply like a 15v battery.

So the next option is to isolate the RF receiver voltage supply from the motors voltage supply and there are numerous benefits behind this, the most notable on the list is no modification has to be done to the Lego IR receiver so any version of the IR receive will work with this RF receiver unit. To accomplish this I will work off the infrared communication and connect with the PF IR receiver by a IR emitter that is apart of the RF receiver unit and separate the RF receiver voltage supply that way. Another advantage behind this is more current for the motor. Also the circuit could be replaced with a fiber-optic communication link for the same results. By using the IR link to transmit data signal from the RF receiver to the IR receiver you could theoretically control multiple IR receiver units with just one infrared signal.

Now the RF receiver will be able to output 4 data signals and each data signal can be assigned each there own channel. Not only will the RF transmitter and receiver will be able to communicate a potential of 4 data signals out one antenna, it will also have the ability to code the RF signal 256 ways.

I will post more when I finish testing everything.

Edited January 7, 2014 by Boxerlego

[Philo]

Looks interesting, but at the moment many thumbnails link to themselves, not to full size images (OK, we can have a look at you BS gallery...)

[Boxerlego]

I appreciate your response Philo. I'm glad that your interested. Sorry for taking so long to reply, I've been busy lately. I linked the top pics to the folders and the pics inside the text to the full size images. The main part of what I posted is still on the drawing board, Though I did forgot to mention at the end of the post that one of the biggest disadvantages as to having a separate power supply for the RF receiver and motors is that if the RF receiver power is turned off what is going to cut off the battery power to the motor when their in motion. I've been thinking about how to solve this problem the most efficient and quickest way I can.

[Philo]

Interesting... I must say I wouldn't have dared to use a voltage divider to power the receiver, but if it works... Good luck for the following work ;)

[S.I]

I've been using these chips to control my motors. They only go up to 1A though.

[clarkdef]

A voltage divider is two resistors, one in series of the circuit and the other in parallel? Right? from the battery source, doesn't the resistor in parallel cause constant drain on battery, I'd say it would, and don't the resistors have to be a certain wattage to handle the pulled current

[Boxerlego]

Interesting... I must say I wouldn't have dared to use a voltage divider to power the receiver, but if it works... Good luck for the following work ;)

Thanks! I'm trying to move away from using the voltage divider to power the receiver and seek better alternatives. I've been thinking lately that it is probably better to build my own speed control unit and control the H-bridge with the Ir receiver not begin in the circuit at all.

I've been using these chips to control my motors. They only go up to 1A though.

Thanks that is Interesting! Is the output voltage really 1.2v to 1.8v, surely that must be a typo as it can handle up to 36v.

A voltage divider is two resistors, one in series of the circuit and the other in parallel? Right? from the battery source, doesn't the resistor in parallel cause constant drain on battery, I'd say it would, and don't the resistors have to be a certain wattage to handle the pulled current

Not exactly, both resistor are in series with the battery. The current flow is 0.0136ma around at a idealistic 15v and from that I was able to calculated out power consumption on the resistors and it appears that they are consuming around a 1/5 watt of power which is not bad consider they are rated for 1/2 watt. Now my battery voltage is not a exact 15V usually it tops off around at 13.6 volts with the AA rechargeable batteries.

[S.I]

If you look at the full datasheet you will see it lists two output voltages, one is for when the TTL logic signal is high, one is for low. High ouput is input voltage - ~1V, low output is ground + ~1V, due to internal voltage drops over the transistors etc, and the overview is just listing the later voltage. This lets me use a 12V power supply to power my circuit, and after the voltage drop the PWM signal is roughly 9V, and this chip contains diodes to prevent inductive damage.

What I have been doing is using an xbox controller connected to me PC with a small program I wrote which maps the stick positions to different motors, and feeds these values to a FPGA via USB. the FPGA then uses these values to determine polarity and PWM duty cycle, and the logic outputs will be fed into the H bridges and then into the motors. I'm still waiting on two last orders of parts to finish this.

[Boxerlego]

Thanks clearing that up for me. Sounds awesome what your doing. I'm looking forward to see this. I've been in the process of making improvements to my H-bridge and been looking at the other methods on how to control one. The recent method I've been successful testing is controlling the H-bridge with just one signal wire output on the Lego receiver.

[BrianZ]

How are you transmitting radio signals out of the IR transmitter?

[Boxerlego]

What I did here is I bypass the IR transmitter and take that data output from the IR controller and send it to the data input on a RF transmitter. Then the RF receiver picks up this signal and send that data to the output pin on the "IR receiver".

[BrianZ]

I just looked at your videos, and the forum topics they linked to. Oh man. I have seen the dark path of my future.

[Boxerlego]

I know it has been some time since I last posted here. But my latest 9V PF project is nearing completion. To give a estimate date of completion, I hope to finish it this week.

Now I believe it's compatible with anything compatible with LEGO PF system so a Sbrick will certainly be able to control my motor driver unit along with the all versions of the PF IR receiver. Now I am probably getting a little ahead of myself here with out testing the final complete unit but if it works well as the breadboard prototypes did then I should have nothing to worry about, hopefully.

Who knows this could be the next LEGO RC unit.

Edited June 10, 2015 by Boxerlego

[Boxerlego]

I have good and bad news at the moment with my latest 9V PF project. The good news is that it works (I got the motor to run roughly around at 1V) but the bad news is that I might haft to extend the estimated time before I show it working at full output. I'm not going in to details at the moment why the motor driver is not working at full output but it I'm to blame for the most part. Nothing too seriously at the moment I've already tested out fixes with the breadboard prototypes. I will post a WIP picture up of my Motor driver circuit hopefully sometime later today. Right now this might be a blessing in disguise by the motor working of 1V from the motor driver. There was lot of power begin dissipated by the transistor and it appears that it was staying relatively cool. Lucky me it didn't smoke up. Now I will say that I have powered the motor at full power but that was only with top half of the motor driver so I know exactly that the bottom side is holding me back from opening it up all the way.

Edited June 11, 2015 by Boxerlego

[Boxerlego]

Here is a wip picture of my Motor driver. As of now I just finished fixing the problem with the motor driver. Now it can power a motor at full output. This is my second motor driver circuit build. This time the H bridge has 4 N channel MOSFET's to power the DC motor and is using a Boost Converter to step up the voltage from the a battery pack to 12 volts.

I just did some motor RPM test and the motor driver was able to drive the XL motor at 380 RPM. Now if it was powered of the direct voltage from the battery box it would be 180 RPM. That is it for now.

[Boxerlego]

Here is a link to my project that I'm using to test out my 12v boost motor driver: http://www.eurobricks.com/forum/index.php?showtopic=109292 Now I just did some test driving with it and it worked out great for the xl motor.

[Boxerlego]

Update: Little over a year ago I made a my own Motor Driver to provide more electric power to the LEGO motors and the modified ones as well. The Motor Driver worked out great powering the Lego motors (M, L, XL) but with the modified ones it didn't turned out how I wanted when you have more then one motor connected. The motor drive did good powering one modified XL motor but once two modified XL motors was connected the starting current was just a little to much for the Voltage Booster to provide which in turn triggers the built in safety device to prevent it from over heating. Now this problem is a simple fix with multiple solutions. Now the easiest fix is just to find a better Voltage booster which I already done, but the Voltage booster is only going to be as good as the Batteries provided. Now one thing they didn't teach you in school is about Batteries and how they really work. You all been misled including myself all your life about batteries and I know why. I know how batteries really work and the truth is this there is no Electrons in the batteries. That is a fact, I've already proved it in LEGO with the Dual PF Battery Pack which I showed everyone how to make. No ignoring this "The Proof is in the LEGO" as I like to say. I want you to understand that the "idealized concepts of perpetual motion" has been the key driving force behind this monumental error with understanding electricity. I know how batteries work and my Laptop batteries benefits from this. I know how to kill a battery and I also know how to keep a battery working in top condition for several years beyond the average expected life span the experts tell you a battery should have. Now I don't care if you don't believe this after all only Mother Nature will determine how the battery is superposed to work and if it works for me then surly it will work for you but that is if you want to understand how to use a battery correctly and not improperly. That why I said the Voltage booster is only going to be as good as the Batteries provided if the batteries are weak then the harder the voltage booster needs to work to step-up the voltage to that point. I've been studying/experimenting with Lithium ion batteries since 2010 and that is the battery I deiced to use because of the higher energy density and higher nominal cell voltage then regular consumer batteries.

[Toastie]

Relax, relax ...

(non rechargeable) ready-to-go batteries are just that: Chemical energy carriers. I guess (and hope) we are teaching >just that< in any "Thermodynamics" or "Electrochemistry" class. The beauty is the equivalent of chemically stored energy vs. electrically available energy. It is not about "stepping up" or whatever means of manipulating the output characteristics of a battery is coming to mind: There is the first law of thermodynamics and there is the second law. And these leave us with: How do we chemically charge up a system so that we get a maximum of electrons moving downhill. >Within< these limits, we can step up/down (etc.) as we wish.

And honestly, we do try to teach exactly this.

Well, I do.

All the best,

Thorsten

[Boxerlego]

Good news everyone, I melted the Batterybox. Now this come to me as no big surprise, Its was only a matter of time when it was going to happen. I will admit that this batterybox had the philo modification on it where you bypass the safety current fuse inside the battery box and now you can see aftermath for the modification. Cool thing about the melted Batterybox is that is still works with the outer two terminals. And this leaves me with my Lego Report. Using the LEGO batterybox with Custom Motors can result in damage to the batterybox electric terminals. So it not a wise decision in modifying the batterybox when certain parts on the batterybox can only handle so much current.

Now due to the Melted Battery terminals above, I decide it was time to make the necessary PF upgrade to my Custom Lego Motor and this is how it turned out.

Relax, relax ...

(non rechargeable) ready-to-go batteries are just that: Chemical energy carriers. I guess (and hope) we are teaching >just that< in any "Thermodynamics" or "Electrochemistry" class. The beauty is the equivalent of chemically stored energy vs. electrically available energy. It is not about "stepping up" or whatever means of manipulating the output characteristics of a battery is coming to mind: There is the first law of thermodynamics and there is the second law. And these leave us with: How do we chemically charge up a system so that we get a maximum of electrons moving downhill. >Within< these limits, we can step up/down (etc.) as we wish.

And honestly, we do try to teach exactly this.

Well, I do.

All the best,

Thorsten

For me there is no electrons dealing with electricity so there is no electron moving up or downhill, Tesla has made me understand that the "energy" is already there. When I said I know how a battery works I'm talking in the unconventional sense in that regard, you know the one we are not taught in school. But that hasn't stop me from learning Electrochemistry and comparing the two understandings. I understand the accepted concepts of "free energy" which is the kind of energy that is readily available to be absorb. Now what I mean by "stepping up" is just my simple way of saying a DC-to-DC converter. In no way am I implying that I have some how broke the laws of thermodynamics here.

[Boxerlego]

Ever since the Lego Battery Box terminals got melted I've been thinking on how to make the PF System better but the more I thought about it the more apparent it appear to be that I just need and get a Hobby RC system. So I did some homework and I came to the conclusion that the LEGO PF system is roughly in the same price margin as a Hobby RC System minus or plus a couple of bucks depending on what you want to achieve. So with that little bit of information I went and got a Hobby RC system and instead of making another thread about the next Chapter of my PF System Upgrades. I'm going to continue posting about it here because I already tested it out by powering all the LEGO PF motors along with the modified XL motor with it and I'm thrilled to say that it works great at powering them. Now the down side currently with the RC system is that it unable to function with the LEGO PF Servo Motor with it but that can quickly be remedy with a Hobby Servo motor.

Here is a quick breakdown of the PF-RC Comparisons I did.

RC: 30$ for a simple hobby RC Radio Transmitter and Receiver

PF: 25$ for a standard 8884 Transmitter and 8885 Receiver

Now you see that is not a big price difference between the two kinds of Transmitter and Receivers so if you just put in the extra 5$ for the hobby RC system you will get way better range and quality of connection, not bad. Now that comparison only appears to be true if your just comparing between RC & PF Transmitter and Receivers but for the Hobby RC system you also need a Electronic Speed Controller for powering the DC Motor then your good to go.

For the battery pack both PF and RC systems offers a nice wide range of selectability in both sizes, prices, and battery types. But here is the common idea that all batteries are 3rd party... Right? So the only difference between Lego PF & RC batteries is that LEGO has a Functional Case to enclose that batteries in and that is it... So if you want to improve the power capabilities with the PF system you need to improve the design of the Battery Case other wise you will end up with a battery box that works as half as good if you intend to push Lego beyond its limits.

With the DC motor this is where the magic happens at. If you want a fast motor you need a motor with less turns of wire, If you want a motor with tons of torque then you get a Drill motor, if you want a Lego motor then you get a Lego motor and if you want both a Drill motor and a Lego motor you need to find a way to have both. Now just like the PF system the RC System has its built in Limitations as well and these limitation work around the inner workings of the DC motor. You think the RC system is able to power a Drill motor as effectively as a RC motor it is designed to work with, Think about that for a moment... but just understand that the RC system is designed to work with the RC motors and not with much larger Drill motors. Now just becasue the RC system is designed to work RC motor doesn't mean that it cant power a much smaller Lego PF motor. Those brushed ESC's can easily power a couple of Lego PF motors easily as the PF system can but the only problem here is the electrical connection between the Lego and the RC.

Now instead of buying a complete RC Car and breaking it, I just went and bought the necessary components for a complete RC-System kit which includes a 2.4 Ghz Transmitter & Receiver, Brushed ESC, Servo and a 540 15t DC Motor, it was well worth the price considering what the prices are for a complete RC Car.

Edited August 18, 2016 by Boxerlego

[Boxerlego]

Well I finally did it and I made this Power Functions Upgrade. Now this PF Wire can connect Lego Motors to any 3rd party RC ESC (electronic speed control) on the market for RC motors. Take note that I added both male and female connectors to both the PF and ESC wires ends, The female connectors modification is not needed for the ESC, the Original factory connectors on the 3rd party ESC will work just fine with the PF wire adapter. I just did both side to complete the look that is all.

Here it is hook up to the ESC below. Hands down, I got to say this is probably one of the best PF upgrades I ever made now the only problem that is left Is the servo controlled Steering more on that later.

[JJ2]

Well I finally did it and I made this Power Functions Upgrade. Now this PF Wire can connect Lego Motors to any 3rd party RC ESC (electronic speed control) on the market for RC motors. Take note that I added both male and female connectors to both the PF and ESC wires ends, The female connectors modification is not needed for the ESC, the Original factory connectors on the 3rd party ESC will work just fine with the PF wire adapter. I just did both side to complete the look that is all.

*snip*

Here it is hook up to the ESC below. Hands down, I got to say this is probably one of the best PF upgrades I ever made now the only problem that is left Is the servo controlled Steering more on that later.

*snip*

Wow believe it or not I have made the exact same thing, different ESC though.

When using mine the motors have a lock feature so they dont coast to a stop does that happen for you?

[Boxerlego]

Wow believe it or not I have made the exact same thing, different ESC though.

When using mine the motors have a lock feature so they dont coast to a stop does that happen for you?

'

That is awesome you made this PF modification. One of the good Idea behind this Mod is that it compatible with different ESC's. This ESC I have can use either a 7.2v or 11.1v Lipo battery and from what I seen with the LEGO buggy I have driving around it stops on a dime pretty much. The Lego motors really didn't display much noticeable coasting when the power is removed from the motors and that was powered from the 11.1v battery. The Motors ability to Coast depends on the drive train to take in and absorb that extra motion that still wants to go forward for the vehicle, Lego has a nice deep planetary gear reduction inside the Lego motor so this in turns also makes the Lego motor act as a decent natural break due to it being a strong drive train for Lego.

Edited September 13, 2016 by Boxerlego

[JJ2]

'

That is awesome you made this PF modification. One of the good Idea behind this Mod is that it compatible with different ESC's. This ESC I have can use either a 7.2v or 11.1v Lipo battery and from what I seen with the LEGO buggy I have driving around it stops on a dime pretty much. The Lego motors really didn't display much noticeable coasting when the power is removed from the motors and that was powered from the 11.1v battery. The Motors ability to Coast depends on the drive train to take in and absorb that extra motion that still wants to go forward for the vehicle, Lego has a nice deep planetary gear reduction inside the Lego motor so this in turns also makes the Lego motor act as a decent natural break due to it being a strong drive train for Lego.

Thanks for the Info, I'm using a 7.2v Nimh battery and the motors seem to have little more torque but that might just be my imagination.

[Boxerlego]

Thanks for the Info, I'm using a 7.2v Nimh battery and the motors seem to have little more torque but that might just be my imagination.

Awesome, I'll try and post more info about this later. Right now I've been thinking about how to incorporate the RC Servo with Lego. I've seen a couple of ideas hashed out including the servo you made. I like the Idea of using a 3rd party servo but the Lego Servo certainly has more to offer when it come to its buildability.