Build a 5/6ch pistol Tx for $120

[clockworks]

Mode 2 is throttle on channel 3 as standard, but, like you say, you can use any channel you like for the conversion. Channels 5&6 need configuring in the software, channels 1 to 4 just work.

For your setup, configure mix1 to use VRA as the ch5 input, always on. Wire your switch and pots to the VRA input.
Do the same with ch6, using the VRB input.
3-position switches will work fine for both channels.
Ch4 for the trail rig dig will also be fine with a 3-position.

Since you are only using these channels for one model, you can probably get away with using resistors, rather than pots, it you want an easier build. Set the servos up, then choose a resistor that gives you roughly the right throw. Fine-tune the throw in the software - there are EPA adjustments for all channels. Once set, you shouldn't need to adjust it, unless you bend something.

I like the idea of a proportional winch control - variable speed, so less risk of snatching and breaking the line. You could adapt one of the original stick assemblies to control this channel, as an alternative to using a wheel.

I've not tried binding more than one Rx to a Tx, but there are several posts on other forums that say it works fine. The Rx gets the Tx's ID during binding, the Tx doesn't get anything back from the Rx, so multiple Rxs should work.

Good luck with the build, and be sure to start a build thread!

[monkeyracer]

Originally Posted by clockworks

I like the idea of a proportional winch control - variable speed, so less risk of snatching and breaking the line. You could adapt one of the original stick assemblies to control this channel, as an alternative to using a wheel.

I've not tried binding more than one Rx to a Tx, but there are several posts on other forums that say it works fine. The Rx gets the Tx's ID during binding, the Tx doesn't get anything back from the Rx, so multiple Rxs should work.

Good luck with the build, and be sure to start a build thread!

Proportional winch control is something that I really wanted, and that no-one locally has. I guess I forgot there will be the sticks leftover from the T6... is one of the sticks a return-to-center type? That would be perfect for it. I could mount that right by the left thumb rest and control in or out while also applying throttle and steering if necessary...

I was thinking that once the two rx's are bound, it would be just a matter of turning the TX on first, and then the truck so the rx would receive the ID from the TX. Model memory is really only for saving the epa settings.

But, what would happen if I turned the TX on, then both trucks though?

For channels 4, 5, and 6, I would probably have a trim-pot board, similar to yours, just in case I need in field adjustments, but hidden in the battery compartment to prevent accidentally moving it.

Doing it this way, I may not make the PDA cable, since like you said, it should be "set-it-and-forget-it" for the end points, but whether I wire resistors or pots, it's the same in terms of ease for me.

I'll probably try and find a cheap case to mod, but at worst, I can use the TQ3 case. What are the dimms of the main PCB? I am also comfortable with plastic work, if you've seen either my Car-PC touchscreen bezel or my current trail rig build.

Of course there will be a build thread, I just need to remember to take lots of pics during the process. I usually get excited to just finish the build and end up with a before and after pic.

[clockworks]

Three of the stick channels are sprung. The whole stick assembly is pretty big, but you might be able to modify it to fit.

If you turned both trucks on at the same time, they'd both respond to the Tx - could get messy!

The main board is way too big to fit in the top of a TQ3, but it might fit in the base. Try and find the "HSP" pistol Tx that Carlos and I have used for our conversions. The PCB fits nicely, and the Tx has a more quality feel than the TQ3.

Know what you mean about forgetting to take pics, but you'll have plenty of time during this build, while you stop and think about solving the minor problems that are bound to crop up.

Are you planning on doing the "4 cell" and "low voltage LED" mods?

[monkeyracer]

Originally Posted by clockworks

Three of the stick channels are sprung. The whole stick assembly is pretty big, but you might be able to modify it to fit.

As long as there's at least one sprung (return to center) stick, that will be just fine...

Originally Posted by clockworks

If you turned both trucks on at the same time, they'd both respond to the Tx - could get messy!

That's what I thought... so, just need to make sure that doesn't happen.

Originally Posted by clockworks

The main board is way too big to fit in the top of a TQ3, but it might fit in the base. Try and find the "HSP" pistol Tx that Carlos and I have used for our conversions. The PCB fits nicely, and the Tx has a more quality feel than the TQ3.

I like the feel of the TQ, but am scouring eBay for a donor pistol... (So I can sell the TQ3 when I am done with it, and recoup some of the cost of building this...)

Originally Posted by clockworks

Know what you mean about forgetting to take pics, but you'll have plenty of time during this build, while you stop and think about solving the minor problems that are bound to crop up.

So, you mean this won't be a smooth, get-it-done in 15 minutes mod?

I might even make a lightbox for the build thread(s) that I'll be making for this... Just take a cardboard box big enough, and cut un-needed sides, lay in a piece of white butcher paper or a white sheet, and mount the lights and diffusers...

Originally Posted by clockworks

Are you planning on doing the "4 cell" and "low voltage LED" mods?

That's the plan. That leaves room for the trim board, and makes it lighter and less batteries to charge.

[monkeyracer]

Originally Posted by clockworks

Are you planning on doing the "4 cell" and "low voltage LED" mods?

What I may actually do now, is use 2 cells from a laptop pack that I've dismantled (Li-Ion 2400mah 18650 sized cells) wired through an extra CCBEC to regulate the voltage back down to 5v.
In a 4-cell nickel pack voltage would be between 4.0V (dead) and 5.6V (full charge) but the tx wants around 5.0v to be "happy".

A 2s Li-on side by side pack would be roughly 37mm x 65mm x 18mm, and about 96g (before wire/heatshrink/connector) Although this can be hidden in the grip or in a end to end stick arrangement (18mm x 18mm x 130mm) since these can charge inside the tx.
A 4s NiMH pack is roughly 49mm x 60mm x 15mm, and about 120g

Both would be about 2500mAh capacity, and roughly the same discharge rate (although the tx won't draw a ton of current) but the Li-ion would last a little longer since it's low voltage threshold would be sufficiently over 5v (and it's regulated with the BEC) and it's got a lower self-discharge, so I could store the transmitter for a week or two without worrying if it's dead or not. As far as low voltage cut-off, I might be able to get a protection circuit from a battery supplier to wire in to prevent over-discharge.

Why go through all this trouble? I could keep the batteries in the hand grip portion of the controller, or end to end in the battery compartment, leaving more than enough space in the battery compartment for the PCB, pots, computer connector and charging plug. Oh, and I already have the Li-ions just sitting around doing nothing. (And I'll have 4 spares for other projects.)

It's going to be after xmas before I get to start my project (waiting on xmas money) but I will definitely post a build thread of what I end up doing.

[clockworks]

The NiMH AA cells that I use (branded "instant") are similar to Sanyo Eneloops. The self-discharge rate is extremely low, certainly not noticeable over a few weeks.
The weight and size saving might be useful, though.

You say that you are going to fit the PC connector in the battery compartment. Be aware that, if you extend the wires, you might get the horrible servo twitching that plagued my build, until I relocated the connector and shortened the wires.

[monkeyracer]

Originally Posted by clockworks

The NiMH AA cells that I use (branded "instant") are similar to Sanyo Eneloops. The self-discharge rate is extremely low, certainly not noticeable over a few weeks.

I like the eneloops, and would have gone with something like that if I didn't have this laptop pack just sitting around.

Originally Posted by clockworks

The weight and size saving might be useful, though.

You say that you are going to fit the PC connector in the battery compartment. Be aware that, if you extend the wires, you might get the horrible servo twitching that plagued my build, until I relocated the connector and shortened the wires.

Everything will be in the battery compartment, including the main PCB, so I won't need to extend any wires other than the control switches, and wheel/trigger wires. (and I guess the antenna too)
This is if I use a TQ for the donor. If I use the HSP, or another donor pistol, it all depends on space, but the plan is to have as much in the battery compartment as possible since I can hide the Li-Ions in the handle if I need to.

[clockworks]

Good point about already having the cells.

When I did my build, the only thing I was scared to do was unsolder the antenna wire. It's extremely small. I imagine that it'll melt and short the shield to the inner conductor if you leave the soldering iron in place for more than a second or two.

[monkeyracer]

Originally Posted by clockworks

Good point about already having the cells.

ya, anyone else doing this would be better off using 4 (or even 5 with a regulator) nimh cells. With these though I can be a little flexible where the cells are located.

Originally Posted by clockworks

When I did my build, the only thing I was scared to do was unsolder the antenna wire. It's extremely small. I imagine that it'll melt and short the shield to the inner conductor if you leave the soldering iron in place for more than a second or two.

That's the only thing I am worried about too, everything else isn't as sensitive as that wire.
Thinking about the work going into this, like you said, it's a lot of hours of work, so if there was a value placed on these, it would be almost triple (or more) the $120 in parts cost. But for that you get a 2.4GHz 6 channel pistol radio which is fully customized to your needs, and flexible for future upgrades.
What would be nice is if Turborix (or whoever makes these originally, or any company for that matter) made a pistol 6ch 2.4GHz Radio inexpensively... But as discussed earlier, they don't see the demand for it, and if they sold only 1000 units, it would not be cost effective.

[monkeyracer]

I just checked the cells from the laptop pack, there are 6 total cells in 3 parallel pairs (3S2P) on one pair, the cells read 0V, completely discharged, totally dead... Maybe that's why this pack was having issues.
The next pair read 2.4 or so volts. Below the minimum, but I might be able to salvage it, but maybe not, the tab became un-welded from one cell (another reason this pack didn't work in the laptop). The last pair measured 3.62V so that pair is still good.

I have at least one good pair, so I will have something to use. If it weren't for that though, I'd get LSD-NiMH cells.

[clockworks]

I've never worked with Lion cells. Do they charge the same way as LiPo, using balance taps?

[monkeyracer]

Originally Posted by clockworks

I've never worked with Lion cells. Do they charge the same way as LiPo, using balance taps?

Crap, I had a whole thing typed up about Lithium Ion (Li-Ion) vs. Lithium-Ion Polymer (Li-Po) but my IE crashed...

Li-Po is just an evolved form of Li-Ion. Li-Po has a higher discharge current capability, higher energy density, and since the electrolyte is held in a solid polymer, doesn't need a hard metal casing, making it lighter.

Li-Ion's charge and balance just like Li-Po, but most multi-chargers (like mine) have a seperate program for them since the LVC is lower than Li-Po. I am going to get a PCM to protect the batteries since they'll be hidden in the casing.

This circuit board protects from over-charge, over-discharge, over-current, and short circuit, all important with any lithium battery. Notice though that the LVC is 2.3V I thought that was low, but almost every LVC that I've seen for Li-Ion is around 2.3-2.5V. Maybe the lower voltage pair of cells I have is fine after all?

In addition to that though, I was going to get a voltmeter like you and meao did, but I like this one:

Mini 99.9V Blue Digital Volt Meter for System Monitoring It runs off the regulated 5V power source, but I can wire the "measured" voltage directly off the battery leads. And it's still pretty inexpensive. There are other places to get it, and they make red and I think green digits, and 4 digits as well (although it's a little bigger). It's only about 2" x 1" for the display area, so not huge. Also, it will measure just the total voltage, rather than blinking between cell voltages, and total voltage.

Still looking for donor pistols, what was the main PCB's dimensions?

[losikid]

on the tq3 the pcb out of the older 6 channel radio can fit in the tq3 at the base with some mods to the main pcb and to the controller itself, if you would like to do it to the tq3 i could tell you some more info on what mods are needed, also i seen you wanted to put the batteries in the handle which will be near impossible because all the wires of the switches and pots take alot of room and need to be ran through the handle

[monkeyracer]

Originally Posted by losikid

on the tq3 the pcb out of the older 6 channel radio can fit in the tq3 at the base with some mods to the main pcb and to the controller itself, if you would like to do it to the tq3 i could tell you some more info on what mods are needed, also i seen you wanted to put the batteries in the handle which will be near impossible because all the wires of the switches and pots take alot of room and need to be ran through the handle

If I use a TQ, the batteries will go in the base, but if I use a pistol that has the PCB in the top portion, I might put them in the handle, but likely they will still go in the base. I may mod the actual case to fit everything when I get it all.

There are some pretty inexpensive TQ2's on ebay, and I'm familiar with how they come apart and go together. If I get a TQ2, I can place the aux channels anywhere I want them.

I'm hoping to order everything by the end of next week.

[losikid]

i used a tq2 for the mod (which i failed)and i planned on mounting my own switches so theres no need for the tq3 unless you already have one laying around

[losikid]

alright, i found another radio i'm thinking about trying it again as soon as i get more $, hopefully i'll be able to get er done right this time and not fry the board, i'm thinking about using 4 of these as batteries http://hobbyking.com/hobbyking/store...4_Cell_w/_tabs beings that they're fairly low in profile and they are rechargeable so i can integrate them into the controller and have more room on bottom, but can this tx handle 13.2 volts, or is 9.9 too low

[monkeyracer]

Originally Posted by losikid

alright, i found another radio i'm thinking about trying it again as soon as i get more $, hopefully i'll be able to get er done right this time and not fry the board, i'm thinking about using 4 of these as batteries http://hobbyking.com/hobbyking/store...4_Cell_w/_tabs beings that they're fairly low in profile and they are rechargeable so i can integrate them into the controller and have more room on bottom, but can this tx handle 13.2 volts, or is 9.9 too low

Those aren't really that small. That's what I was going to use for the T6 pistol. (I have 2 2400 mah cells leftover from a dead laptop battery...) These cells are only 1100mah, but that's over a broader voltage range that the TX is incapable of using.

18650 = the size of the cell 18 mm diameter, 65.0 mm length.

For the price, you might as well get a tx lipo, and a BEC or voltage regulator.

This battery is only 97x37x14, whereas 4 18650 cells would be either 130x36x18 or 72x65x18... Also, 4 18650 cells would be about 240g, vs 95g for the lipo.

The only reason I was going to use the 18650 cells was because they were essentially free. If I were to spend ANY money, it would either be 4 LSD NiMh batteries, with the 4 cell mod, or the lipo I linked to.

Just trying to share the info I considered during my research.


I was just about ready to order the t6 and start modding, then I saw the new Traxxas TQ link 2.4ghz HO 4 channel systems. The only issue is that it seems the 4ch version doesn't have epa and center trim capability on channels 3 and 4. I was thinking it would be possible to rewire the trigger, wheel and switches so that epa could be set for those channels.


In the end, I will probably just get the T6, and build it the way I want. But it comes down to whether I want to do the work of transplanting the T6 into a pistol case or simply re-wire a tq link transmitter.

[losikid]

Originally Posted by monkeyracer

In the end, I will probably just get the T6, and build it the way I want. But it comes down to whether I want to do the work of transplanting the T6 into a pistol case or simply re-wire a tq link transmitter.

Oh i didn't realize they were that big, i'll probably get the nihm, , and the new 2.4 tq is 100 bucks and i found a hk tx for 15 bucks and i've already done all the mods to the radio case so i might as well go with the conversion, and its computer programable

[monkeyracer]

Ok, more research...

The TQ4 HO Link radios are nice, but still limited in their capabilities. So, I'm back to looking into the T6 radio.

I found the Exceed RC version at hobbypartz.com for $44.95, plus $14.95 for a second receiver, and $4.95 shipping from california.

I'll be getting a TQ2 as the donor pistol, but I'll need to mod the steering stops to get the most steering.

I'll probably get 5 LSD NiMhs, wired to the Voltage meter I posted earlier, and through a BEC to regulate voltage to 5V. (Doing this, I won't need to mod, or even include the T6 battery monitor LED.)

Looking at building a parts list for this. So since I won't need a mixing channel like clockworks has, I'll have the channels set up like this:

Channel 1 - Proportional Steering using the Pistol controller's wheel modded for more travel (no epas necessary, my hand on the steering wheel will control travel distance) - Both vehicles

Channel 2 - Proportional Winch control, using a 'return to center' stick from the T6, in line with a 3-pos switch with 470R resistors. (no epa's necessary, will use a mini-ESC for that.) Both the sprung stick and the 3 pos switch will be mounted by the thumb- Trail Rig only

Channel 3 - Proportional Throttle using the Pistol controller's trigger (no epa necessary, but I'll be keeping the TQ's steering center trim) - Both vehicles

Channel 4 - 3 position Front Dig using 470R resistors, and setting epas through the computer. Switch mounted on top of controller. - Trail Rig only

Channel 5 - 3 position Rear Dig (or both front and rear with MOA) using 470R resistors, and setting epas through the computer. Switch mounted next to the steering wheel. - Comp Crawler only

Channel 6 - 3 position switch using 470R resistors, and setting epas through the computer. Switch mounted on top of controller. - May be unused, but might switch lights on and off with a homemade 'pico switch' - Trail Rig only (maybe)

I plan to mount the PCB in the TQ's base, with the mods to cut it down to fit, and the computer connector next to the batteries (no need to extend any wires, preventing any jittering.)
The voltage display will likely go on top of the base, so it's visible at all times. It will double as a "power on" LED.
The batteries will be connected to a Deans connector so I can charge the batteries on my charger. I might use a 3 pos toggle switch to switch between charge-off-on. It's not a big deal either way, but if I do this, I can charge the batts without removing them, and without powering the transmitter the whole time it's charging.
I'll also need to get a couple waterproof boxes for the Trail Rig

Eventually I'll want to make a PDA cable so I can update settings in the field.

So, all I'll need is the TX/RX, donor pistol, some 3 pos switches, 470R resistors (1 watt?), voltage meter, RX boxes, and the 5 batteries. Should come in WAY under $120. Just need to find a good inexpensive place to get the switches and resistors...

Am I missing something in my parts list?

[losikid]

are you getting your batteries at hobbyking, also on another note to make it fit inside a tq you have to cut the board down and cut slots in on each side of the case and take another piece of plastic to each side and cover up the slot, i probably have 4-7 hours with a dremel modding mine and i'm still not completely done, also another question i have is because the handle will be really tight with switches and stuff the wires will be hard to get jamed in there so can i run just one red and one black wire up through there and the signal wires.