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Old Nov 06, 2004, 09:42 AM
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Ontario, Canada
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What is the highest voltage that Hitec receivers can take?

Can they handle 7.2V? Why I ask is, I got a Tamiya ESC in a buggy kit and it doesn't have a BEC in it (cheap *****'s). Tamiya lists Rx brands it's OK with, and Hitec is noticeably absent. The (lousy) instructions say to use Rx that have a BEC. I suspect that means a Rx with a separate battery connector that has regulation on that input. Can the Supreme 8 handle 7.2V on its BATT pins? I know it's not rated for that formally. I am pretty clueless about the ways they do things for cars... Thanks.
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Old Nov 06, 2004, 10:19 AM
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http://www.hitecrcd.com/Receivers/supremeSurfRX.htm My guess is that you might sneak past with 7.2 but if you fry the rx there's no reps no warrs!
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Old Nov 06, 2004, 10:58 AM
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It's very confusing, since Tamiya says this ESC works with all the "biggies" (Futaba/JR/Airtronics Z) except they don't include Hitec, yet the others all rate their Rx at 4.8 - 6.0V too. OTOH, I've read that many (most?) Rx have their own regulators around 3.3V for the receiving circuitry...then I'd worry about the voltage the servos are getting. Some car Rx have a BEC built in, but not *that* many, certainly not the lower-end stuff.

I could add my own 5V low-dropout regulator, probably the best course. And I have a better (proper) ESC on order too. But would Tamiya really include an ESC that's so difficult to use with a "normal" Rx? The info/instructions is very poor considering the possible bad consequences.
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Old Nov 06, 2004, 05:31 PM
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Well, you could always rely on Hitec's 2 yr. warranty. I have several cars (don;t tell my wife!! LOL) and some high draw boats (again... mum's the word!!) and those ESCs have a BEC. My one sailboat runs on 6v with no BEC just fine.
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Old Nov 06, 2004, 05:47 PM
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LOL re the hiding! With the bodies off/open, they can't tell...I think. I'm not sure if they see it's "some RC thing" and then stop really looking, so don't know *exactly* how many you have. Just never have too many of the same type model (boat/car) together at once. Works for me.

Now that I'm at home I'll bench test the ESC for my amusement. Almost certainly won't use it, for now anyway. It apparently works well enough for its unfancy purpose, from all reports. But the question still stands: why doesn't Tamiya consider Hitec Rx "acceptable" for this ESC? Something different about them? Hitec's the biggest brand of car radios around here.
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Old Nov 06, 2004, 05:58 PM
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Marietta, GA
Joined Jun 1999
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Surface Rx's often have BEC's built into them so they can be run directly off the main power battery. This does not apply to any aircraft Rx's.
..a
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Old Nov 07, 2004, 03:23 PM
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While I can't offer positive proof about Hitec and voltage, I can say that I had a recent run-in with that very issue lately and thus have an anecdotal report to make.

I have a giant scale plane that was set up using a new Hitec RX and 6 servos total. I had a glitching problem that just wouldn't go away even after exchanging out the servos and double checking all the usual suspects when it comes to interference.
I knew it wasn't my transmitter, because this same transmitter is set up to fly more than a half dozen models and this was the only plane that was doing the electrical dance. I had set up this plane with a 6volt receiver pack from the beginning.

One of the last things I did was to exchange the Hitec receiver for another brand-new Hitec receiver, and that still didn't solve the problem. As an aside, I'll point out that the glitching occurred whether the engine was running or not.

I already know (and always have known) that a freshly charged 6volt receiver pack can cause temporary glitching due to overvoltage from a FULLY charged pack, but as soon as the pack bled off a bit of charge it would stop.
In fact, that's exactly how my other planes with 6volt packs react. But even on my other planes that DID jitter after a fresh rx pack recharge (not all do), the jitter went away after less than 3 or 4 minutes of use.

So just for grins, I plugged in a different 4.8volt receiver pack to my problematic aircraft, and there was absolutely NO glitching. Feeling confident, I then removed one of the cells from the original 6volt pack I had been using all along to make it into a 4.8volt pack and then plugged this original pack back in to the plane and, again, problem solved!

Now this plane flies rock solid, and the bottom line is that the ONLY thing that made any difference, AND made ALL the difference, is that I changed the original 6volt pack to a 4.8volt pack.

The relevence to this thread is that both of the Hitec receivers I tried were brand new, both glitched on a 6volt pack (even after being bled down a little), and both worked fine on 4.8volt packs.
Since Hitec states that their Supreme receiver will work from "4.8v to 6v", I'm going to have to guess that they DON'T mean "4 or 5 cell packs".
Since a 5 cell pack is considered dangerously low at 6.0 volts, then any 5 cell pack that has enough of a charge to fly safely is putting out too much voltage for a Hitec Surpreme receiver.

That's all I got, take it for what it's worth.

Highflight
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Last edited by Highflight; Nov 07, 2004 at 03:29 PM.
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Old Nov 07, 2004, 06:32 PM
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OK, thanks, I'll be wary. And yes, a 5-cell pack is practically dead at 6V, at least with no load.

The problematical and IMO practically worthless ESC does in fact pass the battery voltage straight to the receiver. I can find no receiver that I'd actually buy that has a built-in BEC...so far that is. Very few surface receivers have them, at least as far as receivers you can buy separately, whether cheap or expensive. Only a few do, maybe it's more common in Japan, and it's very clear by the way things are presented that my Tamiya kit is oriented towards the Japanese market. Hitec has at least one Rx that does, but it's not my preferred DC.

A low drop-out 5V regulator costs less than $2 and can solve the issue very easily, just a nuisance to have to do for the car (little room), but had to make some anyway for other stuff with a Supreme... A series diode or 2 could work too, easier and cheaper but less elegant.
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Old Nov 08, 2004, 08:28 AM
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I think the part that throws people off about what voltage the Hitec Supreme can take is that Hitec says it will operate from "4.8v to 6v".
To many of us, we relate 4.8v as "4 cell" and 6v as "5 cell" and we translate Hitec's stated operating voltage as meaning that the rx will operate with either a 4 cell or 5 cell pack.

However as you know, those nominal voltages for 4 and 5 cell packs are just that; nominal voltages, and they are not the normal "operating" voltages of 4 and 5 cell packs.
So Hitec's statement of operating voltage for the Supreme RX, I have to assume based on my personal experiences, means exactly that; voltage, with no inference to the number of cells in a pack.

Highflight
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Old Nov 08, 2004, 03:04 PM
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I think this is further evidence that Hitec really needs to update its receiver designs.

An increasing number of people are flying 5-cell packs now for a multitude of reasons (faster response, greater redundancy, etc) and most other manufacturers offer receivers that will work just fine on 5-cells and also offer smart computer-based decoders with the accompanying massive improvement in inteference rejection.

Hitec's receivers seem to be very much 20th-century designs trying to operate in a 21st-century environment.

If they put as much effort into updating their receivers as they obviously have in their great range of conventional and digital servos then I'm sure everyone would be much happier.
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