Spektrum TM-1000 - RPM sensor on brushless motor

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ecruz64

New Member
Happy Friday Everyone!!

I've been tinkering with my new TM1000 freshly installed into my Trex-450 and somethings not right with the rpm sensor. First, my heli is on the bench (blades off) and I have linear curves for throttle/pitch on my DX8. I spool her up and with less than 25% collective the rpm readout is over 22K. As I continue to give more throttle it eventually cuts out and the display reads "-----". Granted, I am a newbie and I have a lot to learn, but 22K is way to high for such little stick, right? Also why does it cut out (------)? I'm stumped.

I installed per the instructions and soldered to the motor leads (blue/black).

thoughts? Suggestions?

thanks

Ernie
 
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pvolcko

Well-Known Member
Depending on the motor kv and battery you're running that is about double (maybe a little over) what you'd expect on a linear throttle curve at 25%. Is there a setting for electric vs nitro rpm sensing that might cut the reading in half? Or a motor pole count entry that helps the TM-1000 or Tx scale the reading appropriately?

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Also, it is cutting out because there is a 65k upper limit on the reading. You're probably hitting it around 2/3-3/4 stick.
 
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ecruz64

New Member
pvolcko said:
Depending on the motor kv and battery you're running that is about double (maybe a little over) what you'd expect on a linear throttle curve at 25%. Is there a setting for electric vs nitro rpm sensing that might cut the reading in half? Or a motor pole count entry that helps the TM-1000 or Tx scale the reading appropriately?
Click to expand...

Great question; unfortunately, it's one I don't have an answer too. The instruction that came with the tm1000 are pretty straight forward. I didn't see any tweaking options.
 
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pvolcko

Well-Known Member
There should be a pole count setting in the Tx on the RPM telemetry screen. Set it to 6, I believe, for those motors.

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On the DX7s (and I expect on the DX8) the setting is on the telemetry setup screen in the heli setup area (same area you'd use to program a new model into the Tx). Goto the telemetry setup screen, select the RPM entry, then re-set the RPM entry, it will bring up another screen where you can enter the pole count, ratio settings (so it will give headspeed instead of raw motor shaft speed), etc.
 
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ecruz64

New Member
pvolcko said:
There should be a pole count setting in the Tx on the RPM telemetry screen. Set it to 6, I believe, for those motors.

- - - Updated - - -

On the DX7s (and I expect on the DX8) the setting is on the telemetry setup screen in the heli setup area (same area you'd use to program a new model into the Tx). Goto the telemetry setup screen, select the RPM entry, then re-set the RPM entry, it will bring up another screen where you can enter the pole count, ratio settings (so it will give headspeed instead of raw motor shaft speed), etc.
Click to expand...

Great suggestion, thank you! I'll give it a shot after work.
 
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ecruz64

New Member
pvolcko said:
There should be a pole count setting in the Tx on the RPM telemetry screen. Set it to 6, I believe, for those motors.

- - - Updated - - -

On the DX7s (and I expect on the DX8) the setting is on the telemetry setup screen in the heli setup area (same area you'd use to program a new model into the Tx). Goto the telemetry setup screen, select the RPM entry, then re-set the RPM entry, it will bring up another screen where you can enter the pole count, ratio settings (so it will give headspeed instead of raw motor shaft speed), etc.
Click to expand...

Confirmed. 6 poles! What should I set for ratios & how did you get that information?

Thanks again!!
 
Tony

Tony

Staff member
If you set a ratio other than 1:1, then you will set it to show you the head speed, and not the motor speed. If you would like to read head speed (which is more important than motor speed on an electric), then divide your main gear by your pinion. This will give you a number as shown below.

Lets say you are running a 14t pinion and a 150t main.

150/14=10.714285

You would round that number to 10.71 or 10.72 (dealers choice, but 71 is closer) Then set your gear ratio as close as you can get to 10.71:1
 
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pvolcko

Well-Known Member
I got the pole info off align's site (had to zoom in on the performance graphs of the motor to see the pole count).

Ratio should be set to pinion gear teeth divided by main gear teeth. Both the main gear and pinion gear tooth count should be in your heli manual or you can look on the parts (it is usually labeled on there somehow). I'm not sure if it is expecting a reduction ratio (will be fractional) or a gear advantage ratio (will be > 1) so you may have to play with it and see. Reduction ratio is what I described, divide pinion teeth by main gear teeth. Advantage ratio will flip the division values (or take the reduction ratio and divide it into 1).
 
Tony

Tony

Staff member
Yea westy, you can either set it to read the motor rpm (1:1) or you can set it to read the head rpm (10.71:1).
 
Tony

Tony

Staff member
pvolcko said:
I got the pole info off align's site (had to zoom in on the performance graphs of the motor to see the pole count).

Ratio should be set to pinion gear teeth divided by main gear teeth. Both the main gear and pinion gear tooth count should be in your heli manual or you can look on the parts (it is usually labeled on there somehow). I'm not sure if it is expecting a reduction ratio (will be fractional) or a gear advantage ratio (will be > 1) so you may have to play with it and see. Reduction ratio is what I described, divide pinion teeth by main gear teeth. Advantage ratio will flip the division values (or take the reduction ratio and divide it into 1).
Click to expand...

Um, you need to divide main gear by pinion, not pinion by main gear. If you divide pinion by main gear, you get .09333
 
Tony

Tony

Staff member
Neither of those have telemetry. You need the 7s or the 8. It uses the telemetry module to tell the Tx what the heli is doing.
 
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ecruz64

New Member
Tony said:
If you set a ratio other than 1:1, then you will set it to show you the head speed, and not the motor speed. If you would like to read head speed (which is more important than motor speed on an electric), then divide your main gear by your pinion. This will give you a number as shown below.

Lets say you are running a 14t pinion and a 150t main.

150/14=10.714285

You would round that number to 10.71 or 10.72 (dealers choice, but 71 is closer) Then set your gear ratio as close as you can get to 10.71:1
Click to expand...

Wow! That would have taken me a while to figure out.

Thanks guys, again, a HUGE help!!
 
Tony

Tony

Staff member
That is what we are here for. Each 450 has a different main gear. If I knew what heli model you had, I would have given you the exact ratio.
 
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pvolcko

Well-Known Member
Tony said:
Um, you need to divide main gear by pinion, not pinion by main gear. If you divide pinion by main gear, you get .09333
Click to expand...

That's what I would multiply the motor speed by to get head speed (and a factor of .85 or so to account for inefficiency) so that's the ratio I would normally calculate and use. :)

As I said, divide that into 1 and you get the inverse ratio which is what was needed, apparently. I wasn't sure which one the Tx setup needed.
 
Tony

Tony

Staff member
Actually the Tx reads the exact rpm of the motor so there doesn't need to be an efficiency equation. It goes by the rpm of the motor, it's also a direct drive so if there is an accurate gear ratio, it can tell you within 100 rpm of what your head speed is. And it will display it on the Tx. I love the DX8 lmao.
 
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