Hitec Digitals and Futaba PCM

Hitec Digitals and Futaba PCM
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Hitec Digitals and Futaba PCM - 1/10/2006 4:41:50 AM

gsmarino2000

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From: Loveland, CO, USA
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Mike,

We have had some debate between flying buddies here on the issue of V1.04 Hitec Digitals and the need to have them updated for use with Futaba PCM receivers. We've read through the posts and think we understand, but all of us have a lot of money invested and we want to make sure that we understand the implications correctly:

- As we understand it, the problem is specific to the control signal voltage level and is only an issue when two Hitec digitals are ganged together on one channel of a Futaba PCM reciever which pulls the control voltage below a threshold on the V1.04 servos. Is this correct?

- Since this is a control signal issue, and it has nothing to do with battery voltage, it should show itself on the bench if the problem exists. Correct?

- A person using the V1.04 digitals on seperate channels of the Futaba PCM receiver would have no reason to send in the servos unless he planned to gang two of the servos on one channel in the future. Please confirm if you agree.

- One fellow who had the update done by Hitec Service referred to it as changing out a resistor. To be honest, hand soldering on a surface mount PC board concerns some of us. Can you confirm if that what is involved with the update? Or do they replace the board?

Thanks for the help,
Greg

Post #: 1

RE: Hitec Digitals and Futaba PCM - 1/10/2006 3:08:36 PM

mglavin

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From: Elverta, CA, USA
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quote:

- As we understand it, the problem is specific to the control signal voltage level and is only an issue when two Hitec digitals are ganged together on one channel of a Futaba PCM reciever which pulls the control voltage below a threshold on the V1.04 servos. Is this correct?

Test we ran here at home with an early release v1.04 5955TG required sinking current (0.35 milliamp). This causes the sink voltage on a Futaba R149DP receiver to be about 0.45 volts (two servos on a 'Y' would be about 0.9 volts). The switching threshold on the 5955 was about 0.75 volts. So it's easy to see why they won't work on the 'Y'.

For comparison, the Hitec analog 945 and the Futaba digital 9451 servos have little or no current sink requirement and the pulse sink voltage is zero in both cases on an R149DP

quote:

-Since this is a control signal issue, and it has nothing to do with battery voltage, it should show itself on the bench if the problem exists. Correct?

Yes.

quote:

- A person using the V1.04 digitals on seperate channels of the Futaba PCM receiver would have no reason to send in the servos unless he planned to gang two of the servos on one channel in the future. Please confirm if you agree.

Yes and no. I believe it’s prudent to update v1.04 servos when used with Futaba’s R149DP (the R148DP output is about the same) marginal pulse sinking could be considered a weak link in the control circuit IMO.

quote:

- One fellow who had the update done by Hitec Service referred to it as changing out a resistor. To be honest, hand soldering on a surface mount PC board concerns some of us. Can you confirm if that what is involved with the update? Or do they replace the board?

Yes, a resistor value has been updated and in fact a resistor is replaced. I would worry not about a hand soldered and attended solder joint verses a machine solder joint. SMT = surface mount technology. The procedure for attaching resistors in either circumstance is the same no special procedures are in play for resistors, SMD’s (surface mount devices) on the other hand and multi-layer boards are another story. In its broadest interpretation, SMT keeps components-and their interconnecting leads-on one PC-board surface, rather than feeding the component leads through the circuit board.

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RE: Hitec Digitals and Futaba PCM - 1/15/2006 9:21:46 PM

SU29

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From: Springfield, MO, USA
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Mike:

I'm considering the HS6985HB's for a couple of projects however I'm not sure I fully understand the issue here. I have not used Hitec digitals yet nor have I used the programmer. I use Futaba PCM for all of my planes so this caught my attention.

If I understand this, the servos need to be ver 1.04 for this to work with a wye otherwise if the servos are in different channels there is no problem? Is there a limit to how many of these can used with Futaba PCM at one time? Does this only effect the R149DP receiver or are there other receivers effected?

thanks, I appreciate you clearing this up.
Jeff

(in reply to mglavin)

Post #: 3

RE: Hitec Digitals and Futaba PCM - 1/15/2006 10:18:32 PM

mglavin

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Jeff

Any early release Hitec digital servo revision v1.04 will not function in multiples driven from a single channel with any (as far as I know) Futaba PCM RX (two servos and a wye plugged into one channel for example). This problem is specific to Futaba PCM RX’s.

Second release v1.04 servos work without issue as a component was updated to remedy the shortcoming with Futaba PCM. Any v1.04 Servo can be updated for free by Hitec Service.

What type and how heavy models are you contemplating using the Karbonite geared servos with?

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RE: Hitec Digitals and Futaba PCM - 1/16/2006 3:38:30 AM

SU29

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Thanks Mike, is there a way to tell if the servos have the latest software with out the programmer? I need to find a vendor that has the servos with the latest software, do you have any suggestions? I plan to use them on 12lb planes, give or take a pound.

Jeff

(in reply to mglavin)

Post #: 5

RE: Hitec Digitals and Futaba PCM - 1/16/2006 3:46:13 AM

mglavin

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The best way to determine if there the latest servos is to hook two up to a wye and the Futaba PCM RX, they will work or not.

Why are you contemplating using a wye on a small airplane?

The 6985's are great servos BUT the Karbonite gear-trains have limitations. Be careful with poor linkage geometry utilized to realize extreme throws and vibrations

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RE: Hitec Digitals and Futaba PCM - 1/17/2006 1:02:13 AM

SU29

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Mike thanks, I don't plan to use a wye in fact I never do I use mixing for split elevators and flaperons. I just need to understand the issue in case a situation would come up that would deem necessary to use a wye.

My first choice was actually the 5945's. Do you have a recommendation for a high performance 140 size plane.

Thanks again.

(in reply to mglavin)

Post #: 7

RE: Hitec Digitals and Futaba PCM - 1/17/2006 1:37:05 AM

mglavin

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It kind of depends on the type of plane and your intended abuse for same. Precision, 3D or both? Or maybe heavy metal stuff?

The ultimate servos are presently the titanium geared units. The best of the best so to say. The 6900's are excellent choices as long prudent care is exercised in the application. The 5945's are great too, only problem here is 200-500 flights later the Alumalite gear-train is a problem, model dependant.

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Hitec * Multiplex Field Representative

(in reply to SU29)

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RE: Hitec Digitals and Futaba PCM - 1/17/2006 1:49:31 AM

SU29

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What do you mean by prudent care for the 6900's? I noticed that the programmer is on back order at several sites, when will they be available?

Thanks
Jeff

(in reply to mglavin)

Post #: 9

RE: Hitec Digitals and Futaba PCM - 1/17/2006 2:05:05 AM

mglavin

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As I noted previously the Karbonites have limitations, specifically model weight, vibrations, shock loads and poor linkage geometry places undesirable stress on the gear train. Karbonite is not a replacement for metal geared servos. Specifically the problem with Karbonite is its a very hard material BUT its brittle too...

The Programmers are due in toward the end of the month I'm told, it’s hard to say for sure exactly to many variables in play.

< Message edited by mglavin -- 1/17/2006 3:25:28 AM >

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RE: Hitec Digitals and Futaba PCM - 1/17/2006 2:48:06 AM

SU29

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Mike, thanks for the post, I believe I have it figured out now.

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RE: Hitec Digitals and Futaba PCM - 1/17/2006 3:01:40 AM

SU29

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From: Springfield, MO, USA
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I thought I was done, one more question because I assume that all Hitec digital servos are programmable, is this correct?

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RE: Hitec Digitals and Futaba PCM - 1/17/2006 3:26:13 AM

mglavin

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quote:

ORIGINAL: SU29

I thought I was done, one more question because I assume that all Hitec digital servos are programmable, is this correct?

Yes....

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Michael Glavin
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RE: Hitec Digitals and Futaba PCM - 3/4/2006 12:29:16 AM

sillyness

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Mike... I just sent in 3 out-of-the-box 5955s that had gear-train issues to be recitfied (binding gears).

I just got them back and the resistors in the servos have been replaced in addition to the gears (after Servo City swore these were the latest release servos... friggen liars).

I am using the servos with Multiplex 9ch Synth RXs. Should I worry about this resistor thing with these RXs? Can I Y a modded servo and a non modded servo?

Thanks

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RE: Hitec Digitals and Futaba PCM - 3/5/2006 5:53:23 AM

mglavin