ok so instead of buying a winch servo (it was huge to big for my vic) i got a HiTec digital servo 145 lbs at 4.8 and 170 at 6.0
well i’m running an older 2 channel reciever with the futaba attack sr radio 75 mhz and a 4 cell battery pack (uses just double a duracell)
i plugged in the servo and it would work than freak out and not move than work again. well i got up this morning and had no problems with it, now it says in the package for the servo that i should use a 6 cell Ni-Cad pack and re wire the (BEC)
now is it safe to run this servo on just my 4 cell pack and an older receiver, or should i re route the bec and use a 6 cell ni-cad, if it comes to that i’m just going to return it for a different servo. also why did the servo freak the first time i used it?
please help me out if you know about digital servos, apparently these things suck alot of juice.
i love tinkering with these boats it takes up time i’m sure my girfreind is going to hate it soon
What is the servo model number? As far as I know, the Hitec digital servos should not be run with a 6-cell NiCd pack. This feeds them 7.2V, and I believe they are only rated for 4.8V or 6.0V.
I do not know of any Hitec servo that is specified to work on 7.2 volts. I have all sorts of Hitec and was a consultant for them at one time. I know that some models can work comfortably at higher voltages, but the problem arises when folks connect a 7.2 volt or higher to the receiver. I use a Y-harness on all my winches so the power goes to the winch and then to the receiver but I still use a voltage regulator to reduce the voltage to the receiver to 6.0V.
As I said in the prior post, I use a Y-harness to get the power to the servo directly and not through the receiver. Most receivers have a fuse that pops when the current draw is too high, then when the fuse cools, the receiver begins to work again and so does the servo. Digital servos also take a few seconds to begin running after the power is turned on. Most new digital servos work like analogs without being programmed. If your servo was programmed prior to your purchase or you modified it to make it rotate farther the extra resistance in the feedback circuit could cause it to “Freak Out…do-do, do-do, Freak Out”. Oops! Sorry, I just got stuck in a groove from the 70’s.
well right now i think i’m running a 4.8 volt pack cause its only the 4 AA’s, i was just wonddering if i could jus plug it into my reciever and it would work without problems.
i love tinkering with these boats it takes up time i’m sure my girfreind is going to hate it soon
If you are using an Attack SR AM then you will have a BEC receiver which has a fuse that blows when too much current is drawn by the sail winch. To route the full voltage and battery capacity to the sail winch without going through the receiver first, go online to Tower Hobby or to your local hobby shop and purchase a servo Y-harness. Then you can put a 6.0V battery (5-cell NiCd or NiMH or a 4 cell Alkaline holder) or a 4.8V pack into one of the female connectors of the Y. The other female connector gets the sail servo. The male connector on the Y goes into CH 2 of the receiver and the rudder servo goes into CH 1 of the receiver. You can use a 4 cell rechargable 4.8V pack, but you will not get the max speed and power from either servo. Now, the power from any size battery will go to the sail winch directly and not through the receiver, so the fuse in the receiver will not blow unless the rudder winch is fouled up and jammed.
Going through the specs on Hitecs and matching them to the numbers you gave, you are probably using a 5645 or 5925? You should use a min of a 600maH pack, if you use less and the constant current draw is greater than 600ma, then the insulation on the wires from the battery will melt, regardless whether you use a Y-harness or not.
The servo determines the current draw, the battery has the capacity. So, the Hitec 5645 draws 500ma when run with no load off a 6.0 V battery (400ma off 4.8V). With few lbs of load it will consume 1000ma easily. I have seen high capacity AA alkalines from 1300 to 2700maH and regular alkalines starting at 320maH
the Hitec 5645 draws 500ma when run with no load off a 6.0 V battery (400ma off 4.8V). With few lbs of load it will consume 1000ma easily.<hr height=“1” noshade id=“quote”></blockquote id=“quote”></font id=“quote”>
Hi Steve
I notice that the Hitec data sheet says idle current is 3ma, and “running” current is 400 or 500 as you say. It isn’t clear if this is “no load running”. If it is “no load”, 500ma at 6V sounds rather high! I’d naively expect to see the servo working reasonably hard when it takes 3 Watts to run. And if it is “light load” running, do you have any idea what the stall current might be?
Lester: On which servo? I tried to match the Hitec servos to the 145/170oz.in range quoted and came up with the 5645. They draw 8.8 and 9.1mA at idle and 400/500mA no load running. The initial startup amperage when preloaded was over 2A, the limit of my microammeter. Analog 700’s used to run 3.5mA at idle and 180mA no load running, weigh over twice the 5645 and run slow. I have had initial current spikes with the 700’s servo, preloaded, that are close to 2A as they overcome inertia.
Use the Y-harness as described before. Use 4 high capacity AA alkalines (1300maH or more) or a 6.0V NiMH pack (1000maH or more). Your receiver will be OK if you use the Y-harness correctly because the current drawn by the sail servo will come directly from the battery and not the receiver.
On which servo? I tried to match the Hitec servos to the 145/170oz.in range quoted and came up with the 5645. They draw 8.8 and 9.1mA at idle and 400/500mA no load running.<hr height=“1” noshade id=“quote”></blockquote id=“quote”></font id=“quote”>
Hi Steve
I looked up the “Spec sheet” for the 5645 and 5625 on the Hitec Web site. Both are quoted as 3mA idle, while at 6V the 5645 is quoted as drawing 450mA and the 5625 400mA when “running”.
<blockquote id=“quote”><font size=“1” face=“Verdana, Arial, Helvetica” id=“quote”>quote:<hr height=“1” noshade id=“quote”>The initial startup amperage when preloaded was over 2A, the limit of my microammeter.<hr height=“1” noshade id=“quote”></blockquote id=“quote”></font id=“quote”>
OK! So, it could even be higher…
All the specs for Hitec servos that I quoted I got from: http://www.servocity.com/. I decided to test the models that I install more frequently.
Before business opened today, I tested the 5735, 5645, 5945, 815 using a servo driver and a radio set. After subtracting the current draw of the driver or the receiver from total current draw, I found as much as a 150% variation in idle current and 25% variation in no load running between “so-called copies” of the 815’s and the 5645’s. I have only one each of the 5945 and 5735, if you see the price you know why.
I can attribute the deviations to the production run from which they came and their amount of usage. The early models of the first Hitec digital models did have less torque, drew less current, and have lower holding power than the current versions of the same models. I have an early “pain in the rear end-hard to reset”, broken-in version of the 5645 that I tested against a newer, broken-in 5645; the early version had lower numbers all the way around. I also tested the newer broken-in 5645’s and 815’s vs their never-used, “out of the box” counterparts that came from the same production runs, the brand-new servos had higher current draws probably due to gear “tightness”.
There are many explanations for the differences in the specs listed on the internet or packaging. But, the ultimate question is: “Do they work for what you want to do?”. I have had no problems with 5645 and 5945 when converted to drum winches. I run USOM with a rig about the same real area as the IOM A rig (big roaches on USOM sails). I practice for two 2.5 hour sessions without changing batteries (1000maH). I have raced in the teens and twenties (mph) on a couple of occassions recently and not experienced any failures or lack of power. I have been able to do the same with the Futaba winch (with 7.2V, not 6V), but we are talking $55 and some sweat equity for a 5645 winch vs $150 for a Futaba with less torque and holding power, but a little more speed and a better dead band (as they say in the USA, stops on a dime and gives change).
I found as much as a 150% variation in idle current and 25% variation in no load running between “so-called copies” of the 815’s and the 5645’s<hr height=“1” noshade id=“quote”></blockquote id=“quote”></font id=“quote”>
Hi Steve
Interesting! The published specs are surely pretty “nominal”, then.
<blockquote id=“quote”><font size=“1” face=“Verdana, Arial, Helvetica” id=“quote”>quote:<hr height=“1” noshade id=“quote”>I have had no problems with 5645 and 5945 when converted to drum winches<hr height=“1” noshade id=“quote”></blockquote id=“quote”></font id=“quote”>
Even more interesting! Is this conversion a service you can offer? I’m running the 5735 as an arm winch, but would certainly be interested in a smaller, less heavy unit set up as a drum winch.