Brushed Motor 250w Speed Limit

[ryantanch]

Hi fellows,

I live in Australia and there is a speed limit regulation of 25 km/h for ebikes, right now i have a 250w front hub motor connecting to brushed controller ( not brushless) , i would like to know how can i impose a speed limit with a pedal assist system.

Thanks

 

[Nealh]

If not controller limited then a led or lcd display may be able to restrict the speed.
We need to know which controller you are using and a clear pic (not fuzzy) of the controllers wiring if you have no display connected.

 

[vfr400]

What are you using to control the speed - throttle, pedal sensor, both or what?

 

[ryantanch]

right now i am using a throttle , i would like to convert to a pedal sensor

 

[ryantanch]

@nealth , i have translated the exact controller that i am using

 

[Nealh]

Your controller is a speed controller with no option to wire up a PAS system so you will need a new controller with PAS option.
It will need to be a brushed controller if you can find one.

 

[vfr400]

Controllers for brush motors are nearly all with only the throttle connector. Ones with the pedal sensor function do exist, but they're very hard to find. I couldn't find one at all last time I looked.

You already have speed control on the throttle, so you can limit the speed by a physical stop on the throttle to stop it going above the speed limit or you can cut down the electrical signal from the throttle to get whatever maximum speed you want.

To cut down the throttle signal, you can do it with a simple voltage divider. That's two resistors joined in series. I'd use a 1k fixed resistor and a 1k adjustable one (trim pot or normal potentiometer) . The throttle has three wires, red, black and signal. The arangement is
One end of the fixed resistor goes to ground
The other end is joined to either outside pin of the pot
The cut throttle signal wire end from the throttle goes to the join above
The middle pin of the pot goes to the cut throttle signal wire to the controller

Now the potentiometer will work as a maximum speed adjuster. If you install this arrangement near the controller, it'll be neat and inconspicuous.

If you need it to be more legal, like free from adjustment, you need to start with that arrangement and adjust it to get the right max speed, then measure the pot's resistance and replace it with a fixed resistor of the same value.

Total cost would be about 50 cents. These components are extremely cheap.

 

[Nealh]

Yalu Electric have one with PAS on their web page.
Middle one top line, send them a message.
http://www.yalumotor.com/brush_controller/

Here it is on Aliexpress and cheap.
https://www.aliexpress.com/item/Electric-Brushed-Motor-DC-Controller-24V-36V-250W-Speed-Controller-with-PAS-Sensor-Port-For-Electric/32954217852.html?spm=2114.search0104.3.10.11d91b563QoLyq&ws_ab_test=searchweb0_0,searchweb201602_5_10065_10068_10130_10547_319_317_10548_10696_10192_10190_453_10084_454_10083_10618_10307_10820_10301_10821_10303_537_536_10902_10059_10884_10887_321_322_10103,searchweb201603_16,ppcSwitch_0&algo_expid=85e103f1-0844-44db-b550-8827f02f8569-1&algo_pvid=85e103f1-0844-44db-b550-8827f02f8569&transAbTest=ae803_3

Needs a3 wire pas disc/sensor.

 

[vfr400]

Good find. I book marked it for the future. The problem for OP is that you can't limit the speed on the PAS.

 

[ryantanch]

vfr400 & nealth,

Really grateful for the help ! , all of the solutions mentioned are very good, to abide on the laws i would also need a brush controller with PAS function ( Good Find Nealth ) . I have another question which is am i able to use a potentiometer to impose a speed limit on 25km/h?. I have attached the exact law requirement for a pedelec below.

 

[Nealh]

Not often seen though some ebikes have used controllers with potentiometers, If it is possible to introduce one then it would at least help to comply with the speed limit.

 

[vfr400]

If you're doing it yourself, you can only add a potentiometer to the throttle to limit the speed. The PAS function is on or off, so nothing to adjust.

There is one more thing you can do to your bike to legalise it. You can add an external microprocessor to control it. There are two commercially available ones. There's the Cycle Analyst from Grin, which is very expensive and the Speedict Mercury, which is about half of the price of the CA. Contact Speedict about the Mercury. I'm sure they still sell it, but not easy to find on their website They both accept a PAS and throttle signal that they mix into a single programmable throttle signal.

Any college student that knows coding should be able to knock something up for you for a few dollars using an arduino or PIC chip. You program three inputs. One is analogue 5v for the throttle, two is analogue 5v for the pot, and three is for pulsing 5v for the PAS. The logic is simple.
Set a maximum allowed for the output signal, which will be around 3.5V to 3.8V to give 15.5 mph max.
If input 1 is detected, send it directly to the output only if input 3 is pulsing
If 3 is pulsing, output = the input from the pot up to maximum allowed

The whole thing can be powered by the 5v on the throttle cable. Additionally, you ned a capacitor accross the 5v supply to take off any noise, a pull-up resistor on the PAS signal wire, and most microprocessors can't do analogue output but can do an equivalent PWM output for which you need a resistor and capacitor as a low-pass filter to smooth it into analogue. Any electronics student will know about these things. The arduino forums should be able to help you out with an exact parts list and coding if you ask them nicely.

 

[ryantanch]

@Nealth & @vfr400,

Thank you again for the wonderful advices, looks like ill have some work to do.

Full appreciations goes to @Nealth and @vfr400 for helping me on my case !