What the newest cheap servo hotness?

[Hydrocarbon92]

I got received my first JX PDI-HV5932MG 30KG & JX PDI-6208MG 8kg (my faster vehicles) from AliExpress. The claims:

HV5932MG ($25)
Operating Speed: (6.0V) 0.12 sec/60
Operating Speed: (8.4V) 0.10 sec/60
Stall Torque: (6.0V) 25.2 kg.cm (350oz/in!!)
Stall Torque: (8.4V) 32.3 kg-cm (448.5 oz/in!!)

6208MG ($12)
Operating Speed (4.8V): 0.09 sec/60 degrees
Operating Speed (6V): 0.07 sec/60 degrees
Stall Torque (4.8V): 6.8 kg.cm (94.43 oz/in)
Stall Torque (6V): 8.2 kg.cm (113.88 oz/in)
Estimated @8.4v: 11.1 kg.cm (154.14 oz/in)

6221MG ($10)
Operating Speed (4.8V): 0.18 sec/60°
Operating Speed (6V): 0.16 sec/60°
Stall Torque (4.8V): 17.25 kg.cm (239.55oz/in)
Stall Torque (6V): 20.32 kg-cm (281.89 oz/in)
Estimated @8.4v: 27.44 kg.cm (381.07 oz/in)

I haven't received my digital luggage scale so I can't test power, but I can test speed. I wired up a direct 8.4v feed and the JX servos are fast. Their cheap 6221MG is faster than a Savox SC-0254MG (0.12sec) at 8.4v but a little slower at 6V, so I'm guessing a true 0.14sec at 6V and 0.11sec at 8.4v. Testing the new pair against the 6221MG made it look even slower than it made the Savox look, both at 6V and 8.4V. Either the HV5932MG is faster than rated or the 6208MG is slower, as they were the same speed. I also tested them against a TSX-45, a very common servo here and the 6221MG is the same speed at 6V but a LOT more power, so 8.4v will only improve it. The 6208MG is faster but seems to have similar power as the TSX45.

The only down sides: the 6221MG & 6208MG are a tad taller than normal & none are waterproof. However I conformal coat all my boards so that's not a big deal for me. If you don't like spending $80+ on servos or have a lot of models like me, I think these three are good choices - especially since they work on 8.4v.

 

[TheLetterJ]

It sure would be nice if instead of just listing stall torque at a given voltage, manufacturers would list the max amp draw too. I finally found a listing that showed full specs for the Towerpro MG958 (I have 5 of them currently in service) showing 1.6 amps at 6.0v stall current, meaning that damn near any esc's internal bec can run one worry free. That bit of info would be particularly useful when trying to keep one's overall cost in check by skipping the external bec.

 

[StomperCrawler]

I didn't know the 6221MG and other JX servos could take 7.2v much less 8.4v. Does it say that anywhere or are you just experimenting?

 

[Hydrocarbon92]

Experimenting. The main problems with 8.4v is the tantalum (yellow boxy) caps on the boards & little VR's not liking >8v. Almost every servo I've looked at had chips that could take 12-26V. If the board's VR's and caps can take 8.4v then it's just a matter of how hot the motor gets.

 

[StomperCrawler]

Experimenting. The main problems with 8.4v is the tantalum (yellow boxy) caps on the boards & little VR's not liking >8v. Almost every servo I've looked at had chips that could take 12-26V. If the board's VR's and caps can take 8.4v then it's just a matter of how hot the motor gets.

I'm really interested in the 6221's potential. How much testing will you do with it?

 

[rockhugger]

It sure would be nice if instead of just listing stall torque at a given voltage, manufacturers would list the max amp draw too. I finally found a listing that showed full specs for the Towerpro MG958 (I have 5 of them currently in service) showing 1.6 amps at 6.0v stall current, meaning that damn near any esc's internal bec can run one worry free. That bit of info would be particularly useful when trying to keep one's overall cost in check by skipping the external bec.

That would be nice info, but I think there are too many variables for them to provide that kind of spec information.
The Servo you list is fine running on esc bec delivering an Ass whooping Torque of: 166 oz/in (12 kg/cm) 194 oz-in (14 kg-cm) @ 4.8 & 6.0v respectively. When you get above 290 oz/in is when you start peaking above the typical 3 amp factory bec in a crawler.

A safe rule of thumb is to just overbuild your electronics and enjoy driving you’re model. It’s $20.00 or less now for a ccbec so just install one for 290 & up. If one is determined to put the ceiling right above what the ratings are then I would use the following as a rough guide based on my research and experience.

Torque - bec

0 - 280 - use factory bec
290 or 600 or 800 to infinity - use external bec or direct connect to Lipo.


"thumbsup"

 

[Hydrocarbon92]

A motor's amp draw at stall is usually a fixed number since it's Ohm's law based on comm/brush/winding resistance & voltage. The real variable is BEC output. Is it peak or continuous? Does their peak cover 1-sec or 1-millisecond bursts? What temp does it run at max continuous? Was it really tested or did marketing give the rating?

I'm going to try an 8A Henge BEC for dual 6221's then move it to my Exo and try a YEP 10A (20A max) from Hobbyking. One guy tested the later at 10A for an hour. They output ~7.2v on the closest setting, but you can mod the resistors to increase that.

When I get the scale I'll also connect them to my watt meter.

I'm really interested in the 6221's potential. How much testing will you do with it?

Not a lot, but I'm afraid I messed mine up. Last time I waterproofed them I tried Corrosion-X on/in the motors. Turns out they use a flexible magnet (like a fridge picture magnet) and it swelled after absorbing it. They were strong as hell for a few hours, then the heat swelled the magnet further & friction ground them to a hault. I only ran them at 6.6v then, so it wasn't the voltage.

 

[TheLetterJ]

Aw, hey now, give it a little more credit! Those were the original 958's spec's, while the current (for at least the last couple years) one is no powerhouse, they put out an honest 18kg (250oz) in .18s at 4.8v, and 20kg (277oz) in .15s at 6v. They list the "stall" rating as 20kg at 1.6a at 6.6v. I'm running 2 of them on my 4ws car through a cc bec at 6.6v since my WP860's bec is only 3a/5v and would occasionally brown out. Just a decent aluminum cased servo for $10.

But what my point was about is that esc's internal bec's can have drastically different ratings, seeing 2a, 3a, 5a, 8a, and even 15a on the esc's commonly used in crawlers/scalers. Instead of guessing if our bec is adequate or not, knowing the actual amp draw of each component with allow us to actually calculate our demands. We know an MMX can handle any standard sized servo out there, but can it handle 2 of them? with lights? and a fan? while running a winch? See where I'm going?

So a WP1060/AE2/AE5 can't handle much bigger than my bargain servo with its 2a bec, but the WP860/WP1080's 3a bec can easily handle it with 1.4a to spare. It can't quite run 2 of them though. But can it handle one 2290sg? Knowing the stall current could really help the budget minded choose wisely, afterall, if they're looking to buy a cheap servo, they probably don't want to pony up for an external bec if they don't absolutely need it. Nobody wants to find out the hard way by burning their equipment up either.

 

[Hydrocarbon92]

One thing to look for is "switch-mode BEC", that's the type that uses a mosfet & choke rather than a linear regulator. The switch-mode BEC is essentially what a Castle BEC, are 80-90% efficient, and create very little heat. A linear regulator dumps the extra voltage as heat, so if you're pulling 3A at 6V from a 3S, you're dumping 20 watts (3A at 6.6v) of heat into the heatsink. Most higher-end and 1/8 scale ESC's use a switch-mode BEC.

I use switch-mode BEC's the size of a quarter that can supply 2A continuous & 3A max for my arduino projects. I also use them to power my JX 6221's on my 4ws Wraith, 1 each servo.

 

[StomperCrawler]

One thing to look for is "switch-mode BEC", that's the type that uses a mosfet & choke rather than a linear regulator. The switch-mode BEC is essentially what a Castle BEC, are 80-90% efficient, and create very little heat. A linear regulator dumps the extra voltage as heat, so if you're pulling 3A at 6V from a 3S, you're dumping 20 watts (3A at 6.6v) of heat into the heatsink. Most higher-end and 1/8 scale ESC's use a switch-mode BEC.

I use switch-mode BEC's the size of a quarter that can supply 2A continuous & 3A max for my arduino projects. I also use them to power my JX 6221's on my 4ws Wraith, 1 each servo.

Sound advice.

What quarter size ESC's do you use?

 

[svt923]

It sure would be nice if instead of just listing stall torque at a given voltage, manufacturers would list the max amp draw too. I finally found a listing that showed full specs for the Towerpro MG958 (I have 5 of them currently in service) showing 1.6 amps at 6.0v stall current, meaning that damn near any esc's internal bec can run one worry free. That bit of info would be particularly useful when trying to keep one's overall cost in check by skipping the external bec.

Spektrum provides the amp draw at idle and stall for their new servos, it is a nice bit of information to know.

 

[Yeti guy]

amazing story...
i was driving my yeti a month ago then noticed it wouldnt turn. it just ran the servo freespinning. it was my stock tsx45. been in the yeti for 3 yeats of hard driving....

 

[Hydrocarbon92]

Interesting thing I noticed today, the JX 6221's have the same board as Tower Pro MG958's, except 2 more resistors and a big capacitor. The small VR chips on the MG958 blew out when I tried it on 8.4V, so I swapped in the 6221 board. I can't wait to get my scale for testing. The MG958 seemed a little faster than the 6221 at 6V but maybe weaker, so 8.4V should be interesting.

Sound advice.

What quarter size ESC's do you use?

Not ESC, BEC - technically it's just a step-down switch-mode voltage regulator. MP1584 chips are on the better but bigger BEC's, MP2307 on the tiny model. MP1584 can take 6S input, MP2307 can take 5S input. They work great for my arduino GPS/voltage logger modules. The smallest is the size of a penny. You can adjust voltage from 2-22v (min 2v below input).

Turnigy actually used 2x MP1584's in parallel for one of their old 5A BEC's, which got good reviews.

 

[sportbikeco]

A motor's amp draw at stall is usually a fixed number since it's Ohm's law based on comm/brush/winding resistance & voltage. The real variable is BEC output. Is it peak or continuous? Does their peak cover 1-sec or 1-millisecond bursts? What temp does it run at max continuous? Was it really tested or did marketing give the rating?

???

sort of....

If you are saying same load (weight moved) the servo running on higher V draws less amps for same load.

Yet when you run higher votage it is more capable of higher load so...

 

[StomperCrawler]

Interesting thing I noticed today, the JX 6221's have the same board as Tower Pro MG958's, except 2 more resistors and a big capacitor. The small VR chips on the MG958 blew out when I tried it on 8.4V, so I swapped in the 6221 board. I can't wait to get my scale for testing. The MG958 seemed a little faster than the 6221 at 6V but maybe weaker, so 8.4V should be interesting.



Not ESC, BEC - technically it's just a step-down switch-mode voltage regulator. MP1584 chips are on the better but bigger BEC's, MP2307 on the tiny model. MP1584 can take 6S input, MP2307 can take 5S input. They work great for my arduino GPS/voltage logger modules. The smallest is the size of a penny. You can adjust voltage from 2-22v (min 2v below input).

Turnigy actually used 2x MP1584's in parallel for one of their old 5A BEC's, which got good reviews.

So like one of these 1.8a $1 jobbers?

What kind of capacitor should I use and where to solder it? Would a heatsink help with over-amperage and where to place it? Thanks in advance!

 

[Hydrocarbon92]

That goes without saying, as they don't give willy-nilly ratings like 350oz-in at "lots of volts". They wouldn't state amps at "typical hobbyist voltage", they'd say X amps @6V, Y amps @8.4V, etc.

The point is it will draw the same power when you stall the motor at the factory's test bench with 8.4v or on your truck on the hill with 8.4v (assuming no voltage drop). The highest amp draw from a brushed motor will be at zero RPM. Yes, inrush will be higher but it's so momentary & dependent on your batteries, esc, connectors, wires, etc that it isn't a concern.

 

[robertjpjr]

I just purchased the JX Servo PDI-HV5932MG 30KG $24 with free shipping. 2-5days (So they say, never bought from Banggood)
The question I have is, why do the specs show lower torque numbers?

Stall Torque: (6.0V) 25.2 kg.cm (239.55oz/in)
Stall Torque: (8.4V) 32.3 kg-cm (281.89 oz/in)

When I use a kg-cm to oz/in converter I get 32kg-cm = 444oz/in

These numbers are directly from JX website. So is it 280 or 440? Why the discrepancy?

As a secondary question, what is the range of motion of a standard servo? I am aware of 360, 270, and 180. But of JX website the servo in question has a 360, 180 and a "Standard".
If someone knows, I'd appreciate any answers you provide!


Links, for those interested.
PDI-HV5932MG-180° 32KG 180 Angle High Precision Metal Gear High Voltage Digital Coreless Standard Servo-Ji Xian Technology Co., Ltd..---Ultra RC TECH
https://www.banggood.com/JX-Servo-P...igital-Servo-p-1074872.html?cur_warehouse=USA

 

[durok]

Not sure - but I get this one tomorrow for my Ascender to test out - $19, Waterproof, 270deg, free aluminum clamping servo arm:

https://www.amazon.com/gp/product/B01N0XZOZU/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

DS3218 20KG Large Torque Digital Servo Stall Torque (5V): 19 kg/cm (263.8oz/in) Stall Torque (6.8V): 21.5 kg/cm (298.5 oz/in) Speed : 0.16 sec/60°(5V) / 0.14 sec/60°(6.8V) Operating Voltage: 4.8 ~ 6.8 DC Volts Dead brand: 3μs Weight: 60 g (2.12 oz) Motor Type: DC Motor Gear Type: Copper & Aluminum Working frequence: 1520μs / 333hz Size: 40 x 20 x 40.5 mm ( 1.58 x 0.79 x 1.60 in) Features: - High performance digital standard servo - High-precision metal gears with hard anodizing - CNC aluminium middle Shell - Dual ball bearings Package Included: 1 x DS3218 20KG Large Torque Digital Servo 1 x 25T Adjustable metal servo arm

 

[StomperCrawler]

As a secondary question, what is the range of motion of a standard servo? I am aware of 360, 270, and 180. But of JX website the servo in question has a 360, 180 and a "Standard". If someone knows, I'd appreciate any answers you provide!

I bought a 360 and found that it just keeps spinning; the amount you turn the wheel only adjusts the rate of rotation.

I also bought a 180 and it behaves normally whereas I expected it to rotate 180 degrees, which it does not.

 

[mikemcE]

Where the stop pin is, 180 or so. I know some are programmed for less, unless it’s for a sailboat , then they spin.


Hang up and Drive