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View Full Version : JSHWAA'S H-BRIDGE INSTALL TUTORIAL w/desoldering how-to


Jshwaa
09-19-2004, 02:24 AM
I'm hoping that this tutorial will save some people a little money and me a lot of work. Here is how to install my H-bridge.....please do not attempt it unless you read and thoroughly understand these directions. It wouldn't help to ask me about something that is unclear as well. Just be sure of yourself and your skills. I don't want to be held responsible for someone biting off more then they can chew. So here we go.....

To desolder FET's/Install H-bridge you will need the following tools:

* soldering iron
* solder
* copper desoldering braid
* small precision screwdriver or something of the like
* black electrical tape
* digital multimeter
* skills

Optional and useful:

* "Third-hand" alligator clip stand
* Liquid flux
* static mat w/strap


Take your xmod completely apart, or as much as needed to get the EP completely out. Your motor FET's will need to be desoldered and removed to apply this modification. To do this you'll need to carefully remove solder in a series of "remove then cool" type procedures until the solder is stripped enough to attempt the FET removal.
http://home.insightbb.com/~jshwaa/IM001756.JPG
The "remove then cool" procedure, for lack of better words, is a procedure which you place the copper braid over the area to be desoldered, apply heat to the braid for a matter of 3-5 seconds, then remove heat AND the braid at the same time, then you let the area cool for about 10 to 15 seconds.
This procedure is repeated as many times as it takes until the solder is virtually gone from the FET/PCB pad joining. If you happen to have liquid flux, you can speed the procedure up a tad by using a drop of it to quickly cool off the desoldering area, in which case you wouldn't need to wait the 10-15 seconds in between desoldering attempts. If you don't have liquid flux, then don't worry about it, you'll just have to be more mindful of your heating time and cooling time. Be very careful of the tiny transistor that is near the legs of the FET's. It is crucial that you don't burn, destroy, or remove that transistor. Once you have adequately removed the solder from all of the legs of your FET's, they should look like this, and should be ready to "heat and pry" them off.
http://home.insightbb.com/~jshwaa/clean_off_solder.jpg
This is where the small screwdriver comes in. Apply the heat to all 4 pins of one side of the FET's, and very gently pry up the side of the FET.
http://home.insightbb.com/~jshwaa/IM001758.JPG
If you've removed enough solder and apply heat just right, the FET should lift right up. It is crucial that you don't force the legs too much, because you can rip the pads right off the xmod PCB, in which case you've opened a whole new can of worms. We'll just hope you don't do that. Once you removed both FET's, your xmod PCB should look like this.
http://home.insightbb.com/~jshwaa/clean_off_solder2.jpg
You are now ready to solder the 4 wire signal strand to the xmod PCB.

To solder the 4 wire strand to the xmod PCB, it is very helpful to have a third-hand alligator clip stand. You can have one clip hold the EP, and have the other hold the wire in place, while you solder the wire to the pads.
http://home.insightbb.com/~jshwaa/IM001759.JPG
You should strip a very small portion of insulation off of the ends of the 4-wire strand, that was included in the kit. Then pre-tin each wire end, for a quicker joining and cleaner result. Look up "Tinning" on the internet if you don't know what it is. Solder the wires, in order, from left to right so that they will fit nicely under the EP inside the chassis.
The order from left to right on the xmod PCB is not going to be the same order that they are soldered on the H-bridge, however. We'll deal with that later though. To distinguish the wiring, I found it helpful to put a stripe along the the two wires which go to IC5, with a black marker.
http://home.insightbb.com/~jshwaa/IM001760.JPG
This will make it easier to tell which wire is which when you solder the wire strand to the H-bridge board. The kit includes the 4 wire strand, of which I'd say you should need 6" to 8" of(from EP to H-bridge). It's better to have too much than too little though, keep in mind. Strip the insulation and tin the ends of the wire and you're ready to solder to the H-bridge PCB.
http://home.insightbb.com/~jshwaa/IM001761.JPG
As said earlier, the order of the wiring on the xmod EP is not the same arrangement as on the H-bridge. Here is the arrangement on the xmod EP.
http://home.insightbb.com/~jshwaa/4-wire_strand_joint.jpg
Here is the arrangment on the H-bridge, front and back.
http://home.insightbb.com/~jshwaa/h-bridge_strand_connect_top.jpg
http://home.insightbb.com/~jshwaa/h-bridge_strand_connect_bottom.jpg
Notice how they are different from the arrangement of the xmod EP(not in linear order). You will have to separate enough wire, on the H-bridges side of the 4-wire strand, accomodate that. I'm sorry, but this was unavoidable without making the H-bridge PCB a lot bigger. It's a fairly easy thing to deal with, however. Just make sure you get this right and refer to your black marking on the strand to denote wires IC5 pin 2, and IC5 pin 4(or whichever you marked) The order of these connections and the integrity of the connections themselves cannot be over-stated as being crucial to the H-bridges survival. If one of the connections is faulty or comes loose, there is a chance of blowing an FET. You will definitely lose functionality, but if this happens(wire comes disconnected) you must disconnect power to the H-bridge immediately and secure the connection before reapplying power. This is must that you understand. Use the digital multimeter to check the continuity of each wire to be sure that it is indeed connected to it's appropriate pads on both the xmod EP and the H-bridge, AND that there is no cross-connections from any strand/pad to another. That is very important. Look up "check continuity" on the internet if you don't know what that is. It is very important. Put your EP back in your chassis, being mindful of the signal wires being close to the screw hole for the EP/chassis mount. You need to force the wire to go around that screw hole, then the whole 4 wire strand goes around the side if the EP and up along the side-wall of the chassis and towards the top of your xmod.
http://home.insightbb.com/~jshwaa/IM001762.JPG
Now you're done with the hard part, in my opinion. Refer to the H-bridge pics for the location of your connections to cells and motor. If you've accomplished the signal wire install, then this should be a no-brainer. Just keep your wire lengths in mind because you want to allow a gap in between the H-bridge and the car itself. There's 2 reasons for that, air flow and shorts. If the board is too tightly constrained to the car, there is a chance of the bottom of the PCB shorting on a piece of metal of some sort, whether it be the crystal or the CLL port. Leave enough wire so that the H-bridge can stand-off the car and allow the wires to support its weight above the chassis. You don't want the H-bridge resting on the xmod. Again, better to have too much than too little. This is where your black electrical tape might come in handy, to prevent shorts. On my future installs, I plan on putting a layer of electrical tape on the bottom of the H-bridge PCB, to help insulate and prevent shorting on the motor or what have you. The H-bridge has a ton of current flowing through it at times and a short could prove very destructive to the FET's and your cells. So preventing shorts is more important than anything with this installation. Do everything in your power to prevent them, and implement the prevention into your install with having the gap, or stand-off, and insulating with a layer of black electrical tape. I used silicone caulk on my prototype and it worked really well. It all depends on what you wanna do, but insulating the bottom of the H-bridge PCB, and especially the area where the signal wires are connected, is a must. It might not hurt to encase the entire H-bridge in plastic or electrical tape, but it will prevent the FET's from dissipating heat as well....but it's better than losing the H-bridge to a short.

When you get the motor, cells, and signal wiring taken care of, then you can connect the xmod car's power wires to the same place you connected the H-bridge power wires. You should implement a switch or a connector of some sort to be able to manually shut off power to the H-bridge and car, such as a dean's connector or something. Where you have a wire going across the xmod, from one li-ion(cell pack) to the other, is a perfect place for that switch or connector. If you don't disconnect the cells from the H-bridge after every use, your cells drain. Switching your xmod off will not prevent this. With li-ions it is crucial to have a method of disconnecting the cells from the H-bridge, unless you immediately put the car on a charger and keep it there until you race again. Which is what I do.
http://home.insightbb.com/~jshwaa/Im001704.jpg
I have everything soldered in, no connectors. I don't suggest you do that unless you are sure to keep up with your cells charge with a digital multimeter, constantly. It is very important. Having a connector for the motor is optional. I also have the motor soldered directly to the wiring from the H-bridge. This H-bridge is a high-maintenance endeavor with preventing shorts and keeping your cells from draining. If li-ions get below @ 2.5V, kiss them good bye.

That ends this tutorial. Again, please feel free to ask whatever and suggest a mention of something that I might have left out. I will constantly revise this tutorial until it is all inclusive. Thanks. ~Jshwaa

Jshwaa
10-10-2004, 11:33 PM
After tryin' the install myself, I came to the conclusion that the mammoth wire I had wanted to use was actually too big. I just couldn't fit it all under the hood. I went down to a smaller guage wire and I'm still barely able to fit it in a 350Z body, but that's good cuz the 350Z body is one of, if not the most, room restrictive xmod. As some of you know, you have to glue the side ground effects on if you want to run li-ions. I haven't done that yet, but here's some pics of the finished install with deans connectors, which I highly recommend you use.
http://home.insightbb.com/~jshwaa/Im001804.jpg
http://home.insightbb.com/~jshwaa/Im001805.jpg
http://home.insightbb.com/~jshwaa/Im001807.jpg
http://home.insightbb.com/~jshwaa/Im001811.jpg

StiXxX
10-11-2004, 05:09 PM
this might be a dumb q? but is this h-bridge a replacement for the v1 board that hav gone M.I.A. :-? :D
ALSO what happens to li-ions after they drop below 2.5v
i don't know much about them and i'm looking to finally upgrade to the, so be patiant w/me, thanx in advance :nod:

Jshwaa
10-30-2004, 11:22 PM
The H-bridge I build is not meant to replace the V1. The V1 has a regulator on it as well, while mine doesn't.

If your li-ions go below 2.5V, they are considered damaged and should be thrown away.

SwedishRacer
10-31-2004, 06:02 AM
why???

StiXxX
11-01-2004, 11:05 AM
sorry i havn't gotten back to this my comp died, went to hell, did some dirty work for the devil and then was re born as Crapulous 3000
muhuhahahaha

lol whateva i get wierd sometimes
anyways i want to kno the same thing as swede if u do kno
why r lithiums "DAMAGED" at that point?