Custom H-Bridge (tha MOSFET mod)
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CaboWabo
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lol
so when you get stuck for answers, we're sending over some women so you can get you
on - then you'll be havin some new 
that'll make us all 
so when you get stuck for answers, we're sending over some women so you can get you
on - then you'll be havin some new that'll make us all Dear Life Cereal, Where do you get off? Part of a balanced breakfast and delicious? Who do you think you are? By now you may have guessed I'm speaking ironically and have nothing but good things to say about what you do. Life cereal do not change a thing.
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ph2t
- bitPimp
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BRING EM ON!!!! 
I regards to the original transistors on the PCB Cab's I think we can leave them on. I've done a bit of thinkin' (heh, lol!) and have come up with the following:
How the H Bridge Controls Motor Direction
FORWARD
When the car receives the command to go forward the RX chip turns on the transistor at the end of the dashed blue line, given the way transistors work this allows current to travel through the transistor, like an electrical switch, you give the transistor a little bit of current to turn on and it can let a lot of current through it's gates. The transistor in the TOP RIGHT of the picture turns on as well (although a little differently 'cause it's a PNP transistor, out of the scope of this thread I think). This means the current follows the solid blue line. The motor then turns this way.
REVERSE
When the car receives the command to go backwards the RX chip turns on the OTHER transistor at the end of the dashed red line. The transistor in the TOP LEFT of the picture turns on as well. The reverse of what happens above. The current then travels in the direction of the solid red line. This makes the motor spin in the other direction.
This is how you get forward and reverse directions for the motor.
Given all this, if you take the motor out there will be no current flow at all. The H Bridge might as well not exist for all it matters.
So yes Cab's I think you can pull this mod off without needing to remove ANY parts from the PCB. I'm gonna try this now on one of my Compacts to prove this.
ph2t.
I regards to the original transistors on the PCB Cab's I think we can leave them on. I've done a bit of thinkin' (heh, lol!) and have come up with the following:
How the H Bridge Controls Motor Direction
FORWARD
When the car receives the command to go forward the RX chip turns on the transistor at the end of the dashed blue line, given the way transistors work this allows current to travel through the transistor, like an electrical switch, you give the transistor a little bit of current to turn on and it can let a lot of current through it's gates. The transistor in the TOP RIGHT of the picture turns on as well (although a little differently 'cause it's a PNP transistor, out of the scope of this thread I think). This means the current follows the solid blue line. The motor then turns this way.
REVERSE
When the car receives the command to go backwards the RX chip turns on the OTHER transistor at the end of the dashed red line. The transistor in the TOP LEFT of the picture turns on as well. The reverse of what happens above. The current then travels in the direction of the solid red line. This makes the motor spin in the other direction.
This is how you get forward and reverse directions for the motor.
Given all this, if you take the motor out there will be no current flow at all. The H Bridge might as well not exist for all it matters.
So yes Cab's I think you can pull this mod off without needing to remove ANY parts from the PCB. I'm gonna try this now on one of my Compacts to prove this.
ph2t.
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CaboWabo
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ohh shiat ph2t!
I'm thinking it's gonna work!
you have no idea how much weight just lifted from my shoulders lol
oh yea, thanks for the color coded diagram too, makes it hella easier.
I'm thinking it's gonna work!
you have no idea how much weight just lifted from my shoulders lol
oh yea, thanks for the color coded diagram too, makes it hella easier.
Dear Life Cereal, Where do you get off? Part of a balanced breakfast and delicious? Who do you think you are? By now you may have guessed I'm speaking ironically and have nothing but good things to say about what you do. Life cereal do not change a thing.
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CaboWabo
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ph2t
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Heya Modjo good to see ya here man, and welcome to THE place.
UPDATE:
After some testing yesterday I've found that the current design has issues. For some reason the output of the FETs I use aren't getting the same oompf (technical term, lol!) as the FETs from the german version of this mod. This is really strange because on paper the FETs I use are meant to be better than the german selected FETs. Oh well, more testing needs to be done. So sofar the german version of this mod is still the best one out there......
Also the other problem (too many @$#^ problems! arghhhh!) is that if I leave the original transistors in, the voltage to drive the FETs is a max 0.7V. The FETs I've used need more than that to switch on. I've done some research and found some other FETs that WILL turn on at the low 0.7V level. Just have to wait a week for delivery.......
So turn in next week at the same battime on the same batchannel.......
UPDATE:
After some testing yesterday I've found that the current design has issues. For some reason the output of the FETs I use aren't getting the same oompf (technical term, lol!) as the FETs from the german version of this mod. This is really strange because on paper the FETs I use are meant to be better than the german selected FETs. Oh well, more testing needs to be done. So sofar the german version of this mod is still the best one out there......
Also the other problem (too many @$#^ problems! arghhhh!) is that if I leave the original transistors in, the voltage to drive the FETs is a max 0.7V. The FETs I've used need more than that to switch on. I've done some research and found some other FETs that WILL turn on at the low 0.7V level. Just have to wait a week for delivery.......
So turn in next week at the same battime on the same batchannel.......
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CaboWabo
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I have faith in you ph2t, you'll get it.
here's something small to get the thinking cap going lol
here's something small to get the thinking cap going lol
Dear Life Cereal, Where do you get off? Part of a balanced breakfast and delicious? Who do you think you are? By now you may have guessed I'm speaking ironically and have nothing but good things to say about what you do. Life cereal do not change a thing.
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ph2t
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Well I've made a bit of headway this evening..... I managed to replace the DC-DC converter on the BitChar-G PCB from a 3V one to a 5V one. This had an effect in two places, one I didn't even realise at first:
1) The FET's now turn on fully, yeah!!!!
2) The range of the car has increased!!
Here's a pic of the BEAST(tm)
Also here is some video of my tests. The car on the left is my FET version. The car of the right is the German FET mod version. As you can see from the video they are matched dead-on. At the end of the clip is a three-way comparison including a unmodded chassis. The order for that is Ph2t-FET, un-modded, German-FET. The differnece is quite amazing. Get the video HERE (DivX). All the cars were 2.2 Tomy's, softs & orange gears.
At the moment the mod is not where I want to be long term. I want to be able to do this mod with minimal mods to the original PCB. I'm a freak so it doesn't matter to myself but you laypimps might have issues......
Keep in mind fellas that Micro_Amps is doing this mod for people over at Ausmicro.com, check out this thread Getting a BCG MOSFET mod done. This is the benchmark I'm using for my version of the FET mod. For $20 USD (I think) you ship the car to him, he mods it and sends it back, quality work as well.
More to come.
ph2t.
1) The FET's now turn on fully, yeah!!!!
2) The range of the car has increased!!
Here's a pic of the BEAST(tm)
Also here is some video of my tests. The car on the left is my FET version. The car of the right is the German FET mod version. As you can see from the video they are matched dead-on. At the end of the clip is a three-way comparison including a unmodded chassis. The order for that is Ph2t-FET, un-modded, German-FET. The differnece is quite amazing. Get the video HERE (DivX). All the cars were 2.2 Tomy's, softs & orange gears.
At the moment the mod is not where I want to be long term. I want to be able to do this mod with minimal mods to the original PCB. I'm a freak so it doesn't matter to myself but you laypimps might have issues......
Keep in mind fellas that Micro_Amps is doing this mod for people over at Ausmicro.com, check out this thread Getting a BCG MOSFET mod done. This is the benchmark I'm using for my version of the FET mod. For $20 USD (I think) you ship the car to him, he mods it and sends it back, quality work as well.
More to come.
ph2t.
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ph2t
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Hey Modjo,
the DCDC converter is based on the NCP1402 chip from www.onsemi.com. Here's the circuit:
The datasheet is HERE.
I removed the onboard converter, the diode and the inductor and in the place of them I put the circuit above.
ph2t.
the DCDC converter is based on the NCP1402 chip from www.onsemi.com. Here's the circuit:
The datasheet is HERE.
I removed the onboard converter, the diode and the inductor and in the place of them I put the circuit above.
ph2t.
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maximan
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ph2t
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Max, I would still reccomend you get the job done by Micro. My first FET car was modded by him and it is a quality job. It's his mod I'm using the benchmark mine, as shown in the videos posted in this thread. My FET mod is more along the lines of a self install, you need the soldering skillz for it. But I got a while to go yet before I start sellin' tha product..
ph2t.
ph2t.