In line voltage regulator/step down devices

[Phil Woollard]

A little help please guys, after some reading it seems to me that it might be possible to place a voltage regulator/step down device in line to the motor ( there are many available on Ebay for not much dosh) would this work after the speed controller and obviously before the motor, thus reducing the voltage and so reducing the motors rpm's and therefor effectively giving the model a lower gear ratio?
The current would rise as the voltage went down...but no big deal?
The TX stick throw would then be able to go to max and so give me full throttle but the motor would be turning more slowly?
Is this plausibly?
Would the regulator/step down device run when the DC input voltage changes polarity as we select reverse on the stick?
Would the Armortek speed control unit be able to cope or would it not be affected?
So many questions!
Phil

[Adrian Harris]

I cannot see this working.

All voltage regulators work by using feedback from the output voltage to keep it at a static value. If you check out ebay, there are millions of cheap buck/boost voltage regulators, but they all take a variable input and produce a fixed output. If you take a 24V in / 12V out buck regulator and only feed it 12V, it won't produce 6V, it will probably stall (electronically) and produce nothing.

It may be possible to build a high power voltage follower, so that 24V in gives 12V out and 12V in give 6V out but that's not something I've ever seen.

Diodes give a fixed voltage drop of around 0.7V, so in theory, it would be possible to insert a chain of them into the motor cables, but:

a) you would need a chain in each direction, so that the tank could still move backwards
b) they would need to be rated at 100A
c) they would affect the circuit between the motors and the drivers

The Motion pack is already a very capable variable power supply, where the effective output voltage is firmly based on the RC input. I would concentrate on making the input do what is required, so that the Motion Pack does the hard work of producing the power.

The problem with having a fixed gear ratio between the motor and the sprocket is that any reduction in the power to the motor will cause a reduction in the torque. With a good low ratio gearbox, a King Tiger could probably climb into a car without needing ramps!

Adrian.

[Steve Norris]

Hi Phill
Try adjusting the servo range on thr tx. 50% range should give you half speed at full stick deflection.
Regards
Steve

[Gerhard Michel]

Hello Phil,

I think all you need you already have with an electronic speed controller (ESC). It is not good to reduce the voltage of a motor because this also decreases its torque and / or increases its current consumption. What you need is reducing the rpms by holding the high torque, and this is achieved by using a pwm regulator, which ever gives the full voltage to the motor, but in 'time slices', in pulses. E.g. if you give the full voltage for 10 ms to the motor, then a pause of also 10 ms and so on, the motor will reach half the rpms at full torque!

If you will permanently reduce the max. rpms, you should only reduce the resulting maximum servo range per programming your TX, like Steve said.

[Phil Woollard]

Ok Gerhard/ Steve, The TX that i am using is the futaba 7c 2.4ghz, Looking through the manual...page 33 goes into dual/triple rates and exponential, am I in the right section as this deals with adjust-ability in % of range ie neutral stick is 0% , full left is 100%, full right is 100%?
As you would expect everything refers to aircraft modes.
I use the two stick driving method so throttle and elevator for left and right tracks respectively.
The idiots guide is good for me

[Steve Norris]

Hi Phil
That sounds like the right area to be adjusting. You will have to adjust both throttle and elevator the same amount if you use dual sticks for driving, don't forget to adjust in the reverse direction as well .
Regards
Steve

[Gerhard Michel]

Hi Phil,

each channel of your TX should have something as a 'range termination menue' and a 'range adjust menue'. Both values should show + - 100 % when initiated. The range termination ist not needed here and should remain at 100 %.

Now put your model on a stand where track links can move freely. Then put one stick (i.e. the left) to 'full vorward' and hold it tight. One track link will run excessively. Then open the menue 'range adjust' for this channel and start to reduce the shown value (100 %) step by step. The rpms will fall accordng to the falling value. When enough, stop reducing, notice the reached value and store the settings to this channel. Please remember that this was only one direction of one track link! Then you can switch off the model, because the other settings can be made at the TX only by using the noticed value. Then transfer the noticed value to the three other possible ranges 'left full backward', 'right full forward' and 'right full backward'. Now your tank will drive as strong as before, but much slowlier!

[Phil Woollard]

Thanks mate I shall have a go and let you know how I get on, I have domestic earth leakage faults at the old homestead at present so I am running around from building to building trying to isolate the fault many thanks guys for the info cheers phil