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Old Dec 22, 2002, 04:17 PM
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Is this a easier work or would I have to redesign a complete section ?
The changes are usually mininal. Worst case would probably be just an inductor, the adj coil and a couple caps.

However, I do not have a clue what the values would be or how they are ID'd on your Rx. You are on your own.

RC-CAM
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Old Dec 27, 2002, 05:49 AM
Faroe Islands/Germany
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Hi RC-CAM

I once again had a look at your website and it really is a fantastic source for bit converters

I have a question that you might be able to answer - it has relation to another question you kindly answered in another forum:

Would it be possible to re-engineer the h-bridge motor output so I just get four outputs? Then I could hook up the RX to a L293 dual h-bridge and control two motors in forw/rev.

This might also be useful for powering larger blimps.

TIA

Michael
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Old Dec 27, 2002, 11:04 AM
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Would it be possible to re-engineer the h-bridge motor output so I just get four outputs? Then I could hook up the RX to a L293 dual h-bridge and control two motors in forw/rev.
It is not possible to get four independent outputs. However, you could use one high current H-bridge or several lower current bridges to power multiple motors at the same time.

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Mr. RC-CAM
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Old Dec 27, 2002, 12:46 PM
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I was thinking of 4 on/off outputs in total with the two one that are already present for left/right steering. I think it should be possible?

Michael
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Old Dec 27, 2002, 02:52 PM
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I think it should be possible?
It depends on what you have in mind. You cannot have four independent outputs.

The internal logic in the RX2 chip prevents both outputs of a control pair from being used at the same time. The issue is that when "left" is used, "right" cannot be activated. When "fwd" is used, then "rev" cannot.

When thinking in terms of a modern R/C system, the four channel Bitcharger radios are best described as a two-channel system. If this was the 1960's, then it would have been similar to a four channel Reed system.

RC-CAM
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Old Dec 27, 2002, 03:04 PM
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I am aware that I can only use two outputs at a time but this is also exactly what I need. It will be used for tank type steering so, a combination of forward and right will make the tank go forward, reverse and left will make the tank go in reverse. I will not want to have left/right or forward/reverse on at the same time anyway - the h-bridge will not like it.

I guess I can just find the outputs with a DMM and then hook it up to a L293.

As previously stated, this could work for steering a blimp; although altitude control might prove a bit difficult (the cheap ufo's that are available just have the motors at an angle so climb/descent is controlled with forward/reverse thrust.

Michael
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Old Dec 27, 2002, 03:58 PM
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I guess I can just find the outputs with a DMM and then hook it up to a L293.
Yup, what you have in mind is right up the BitChar-G's alley.

RC-CAM
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Old Dec 27, 2002, 08:41 PM
It's a spiderweb of knit lines
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Mr.RC-CAM
Your web site is very impressive! I've used many of your ideas but am having trouble in one area. I'm attempting to lighten the rx by removing the DC-DC parts. I've tried on 2 different rx's and they don't work properly, they seem to glitch more than before. I'm using a 145mAh Li-Poly and have connected V+ to the + of where the big cap was. Do
you have any idea what I'm doing wrong?
Mike Cross
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Old Dec 27, 2002, 09:05 PM
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Mike,

You must leave the DC-DC's schottky diode installed (do NOT remove it). The only components you should remove are the NPN transistor, inductor, and the large electrolytic (if used) that is on the "battery side" of inductor. Place a jumper wire across the inductor pads.

Battery voltage must be between 2.5V and 5V, under load. Never allow the voltage to exceed 5V.

Make sure that you have at least 47uF on the cathode side of the schottky diode. A .1uF ceramic should be across the battery input on the PCB. If power supply noise is really bad, you may need to re-install the inductor for additional filtering.

Here is how I would attack this:
(1) I would start with a stock BitChar-G Rx (clone or Tomy brand). I would then operate it on the single LiPo cell to verify that all was well. I would test it with the motor on and off, at various ranges.
(2) Then I would remove the DC-DC's NPN transistor and verify that all was well.
(3) Then I would remove the inductor and jump the pads, and verify all was well.
(4) Then I would replace the big cap on the battery side of the inductor with a .1uF ceramic, and verify all was well.

If at any step you get into noise issues then STOP and work out a solution before moving on.

Mr. RC-CAM
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Old Dec 28, 2002, 12:14 PM
It's a spiderweb of knit lines
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Thanks Mr.RC-CAM,
I'm working my way thru it, I'll let you know how I do.
Mike
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Old Jan 02, 2003, 03:43 PM
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Yikes, the new BitCharger hack web page has drawn soooo much additional web site traffic that I got nailed with a nasty "excess bandwidth" charge.

Rather than remove the page, or reduce the image sizes to lower the page's byte count, I've moved the BitCharger info to my idle AOL web site. The RC-CAM Project Page's link to it has been updated, so the change is transparent to those that visit the main RC-CAM site.

BTW, is anyone actually using the published BitChar-G technical info or are your visits mainly driven by curiosity?

Regards,
Mr. RC-CAM
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Old Jan 02, 2003, 04:18 PM
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Using it

It is a goldmine of info and I have saved it for off-line browsing.

Thanks for your time and effort.

Michael
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Old Jan 02, 2003, 04:28 PM
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I have saved it for off-line browsing.
That is an excellent idea. It sure helps my end out.

I performed some edits to the page a couple of days ago. You might want to save it again to get the updated info.

RC-CAM
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Old Jan 03, 2003, 02:33 PM
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The schottky diode can be removed, just drop a jumper across its pads, like you do for the removed inductor.
The NPN transistor is actually a DC-DC converter controller IC.

Simon
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Old Jan 03, 2003, 03:18 PM
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The schottky diode can be removed, just drop a jumper across its pads, like you do for the removed inductor.
I suggest it stays in. If left in place, it will help improve the conducted noise immunity of the Rx's power buss.

In conjunction with the large cap on its cathode, it acts as a charge pump during the heavy voltage spikes on the battery supply leads. This is an old trick that works well on low current loads (the Rx IC draws very little current).

For info on the DC-DC circuitry, please see my web page. The "NPN" really is a transistor -- the RX2 RealTek chip has the DC-DC controller built into it. It is a very clever design. However, the less popular Shenzhen SM6135 chip does require an external DC-DC control circuit.

Regards,
Mr. RC-CAM
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