Considering open source Cycle Analyst/APM

[sal_park]

Hi,

noticed this thread yesterday. I've been building something which is very similar to what you're talking about, although not quite the same (linky). I'm using an arduino, 4x20 LCD display and other bits and pieces. All the code (and there's quite a bit!) will be released as open source but I'm holding off for the moment until the project is in a working status - very close but not quite there yet!

Here are some teaser pics:

View attachment 1

you might be interested to look at this thread which give all the details of the above project.

sal_park

 

[CanadianWinters]

I accidentally found this voltage regulator on ebay http://www.ti.com/lit/ds/symlink/tl783.pdf
I ordered a couple and I will try to power the whole thing directly from the battery pack. This will make things a bit tidier (less wires..no need for external battery)

So I did some research and other testing.

The tl783 works well, but needs a 15mA load otherwise there is no regulation at all! I will try to mount it on the board during the weekend.

8)

 

[CanadianWinters]

Today I had some time to solder the TL783 on the board.

Finally my wattmeter/open source CA is self powered!

The TL783 heats up a little bit too much for my taste, but so far it works. I tested it for one hour and it worked well despite the heat. Maybe I should try a better heatsink.

 

[pendragon8000]

nice one Squzzete
had a sus of this data sheet. it looks like 125V is the max for that Vreg chip. so that would handle the vast majority of ebike rigs out there.
and 700ma max output is reasonable.

I was thinking about doing a small moduel with a few built in white LEDs, 5mm or 1w smd style. so if mounted on the handle bar it can be used as a front light to. that Vreg would give 7.5 watts at 10v , prety sweet hey.

I have to get some work done on my car so im hesistant to buy a bike and parts for it. sorry to be talking the talk but walking it, I'll probly get my friction drive bmx happening in a week or two. get some annual leave payed out and it's game on
Idea: ramp power from stationary to a set speed, so:
if speed <=S1 then powerLimit = lowlimit
If speed >=S2 then powerLimit = highlimit
else powerLimit = (speed-s1)/(s2-s1)*(highlimit-lowlimit)+lowlimit
this would help prevent ineficientcy at low speed, sort of like throttle ramping for efficiency on the ca v3 but governed by speed. this would be great for pumping high power through a relitively small motor. btw it took my about 20mins to work out that equation. i think it's right but please correct me.

 

[CanadianWinters]

Idea: ramp power from stationary to a set speed, so:
if speed <=S1 then powerLimit = lowlimit
If speed >=S2 then powerLimit = highlimit
else powerLimit = (speed-s1)/(s2-s1)*(highlimit-lowlimit)+lowlimit
this would help prevent ineficientcy at low speed, sort of like throttle ramping for efficiency on the ca v3 but governed by speed. this would be great for pumping high power through a relitively small motor. btw it took my about 20mins to work out that equation. i think it's right but please correct me.

Hi Pendragon,

maybe I didn't have enough coffee this morning, I don't understand what you would like to do with the "throttle output" mod you are describing there.

If it's just a speed limiter (and of course Watts and Amps are limited at top speed as a consequence) I suggest using a potentiometer on the throttle wires. I am using this method on my e-bike and works great. This way even if the APM/CA is not working, the ebike is not affected.

8)

 

[pendragon8000]

The idea is that with a small 1kg motor that will just make heat and burn out if driven too hard from stationary, having the power increase as the speed gets to a preset value.
Eg
500watts < 5kph
increasing to 1kw up to 15kph
And staying at 1kw >15kph

All the values could be changed to suit motor and application.

 

[CanadianWinters]

Now I see what you are saying.

I think it can be done like this:

"If speed < X
If Amps > Y
pwm output = x"

and so on. I am not actually sure it will work but I think that's the logic to follow.


8)

 

[pendragon8000]

Yeah that's it. The only thing is there would need to be a power up ramp after a certain speed so it not suddenly giving double the power with full throttle as the low speed limit is passed. Could be done with a for next loop to increase it over time eg 1 second. Or proportional to speed as in the equation above.

 

[pendragon8000]

Finally got my arduino and LCD shield. Time to start playing
I should have bit the bullet and got a out runner and controller to put on a bike. Oh well.
Anyone wana report on there experiments?

 

[corim123]

Finally got my arduino and LCD shield. Time to start playing
I should have bit the bullet and got a out runner and controller to put on a bike. Oh well.
Anyone wana report on there experiments?

I'm curious to see where things have gone as well. I'm always up for the cheaper/DIY version of a project.

 

[pendragon8000]

?
So I intend on current limiting with arduino.

There are 20amp hall effect current sending modules. But I'm looking at making a shunt and op amp current sensor.
anyone have thoughts about what op amp if to use?
Need linear conversion of 200mv range to 5v
I'm looking at this one
http://www.jaycar.com.au/productView.asp?ID=ZL3974
Thanks for any help.

 

[sal_park]

what about this to measure current ?

 

[pendragon8000]

Yes. That's perfect! I'm looking at the 100Amp bidirectional with 20mv / a . The arduino has analog input with about 1000 increment of .005v or 5mv so 4 increments of measurement per amp would make it sensitive to .25 amps. Bidirectional would only be useful for regenerative brakeing or monitoring charging. Otherwise there is double the sensitivity for uni-directional.
Say 50v 50A is the limits that would give an accuracy of 12.5 watts minimum.
Thanks a lot Sal_park.

 

[CanadianWinters]

@ Pendragon

I use the same ACS758 in my project. I bought the 100A unidirectional but looking back I would go for 50A bidirectional to monitor charging and eventually (when I will implement it) regen. I don't know what kinda current you get on your controller but I ger 44-45A peak on my most powerful setup (20S li-mn). So I think 50A will work for most mid-low power setups.

 

[pendragon8000]

Yeah the charging option is attractive. Regen isn't worth worrying about other to know its working IMO.
I was thinking sacrifice some accuracy and gain robustness by going 100amp. But yeah I'm gunna test it on a 1kw friction drive.
Also I'm going to start working with a friend in the near future, on using an Android device as the HUD (head up display).

 

[sal_park]

@ Pendragon

I use the same ACS758 in my project. I bought the 100A unidirectional but looking back I would go for 50A bidirectional to monitor charging and eventually (when I will implement it) regen. I don't know what kinda current you get on your controller but I ger 44-45A peak on my most powerful setup (20S li-mn). So I think 50A will work for most mid-low power setups.

I've got a 500w motor and keep the current below 30A as this is the burst limit for my bsttery.

If you use an arduino with his sensor it's worth looking through the example code I linked to above because you will NOT get good results by assuming Vcc is 5v.

Finally, I've implimented a current limit on my project (bangxiety meter) using human feedback - when the current drain goes ovet a set value a buzzer will sound for a few seconds. This has the added advantage of teaching when you draw high current. I can try and do a quick video if you want.

 

[pendragon8000]

@ Pendragon

I use the same ACS758 in my project. I bought the 100A unidirectional but looking back I would go for 50A bidirectional to monitor charging and eventually (when I will implement it) regen. I don't know what kinda current you get on your controller but I ger 44-45A peak on my most powerful setup (20S li-mn). So I think 50A will work for most mid-low power setups.

I've got a 500w motor and keep the current below 30A as this is the burst limit for my bsttery.

If you use an arduino with his sensor it's worth looking through the example code I linked to above because you will NOT get good results by assuming Vcc is 5v.

Finally, I've implimented a current limit on my project (bangxiety meter) using human feedback - when the current drain goes ovet a set value a buzzer will sound for a few seconds. This has the added advantage of teaching when you draw high current. I can try and do a quick video if you want.

Yeah that sounds really interesting. I'm sure many ppl would benifit from seeing some more specifics.

 

[CanadianWinters]

I guys, I am still working on a circuit to integrate a sort of low voltage alarm into the open source APM/CA

This is what I accomplished today using a cell-log:

[youtube]UQhINgC-qhQ[/youtube]