You don't know til you try . . .

Mobility Scooter eCarts conversion

, posted: 30-Jun-2014 19:58

After seeing how cheap mobility scooters were going for I decided to try and turn one into a little electric cart for the 'kids'.
Mechanically they would be worlds better than the plastic kids ride on toys you can get.


I wanted a 4 wheel model, 3 just wasn't going to cut it.

Picked up one for $100 ish.

Cosmetically it was a little rough.
Frame OK.
Batteries were dead.
Controller had a fault.
Motor OK.
Tyres OK.

The important bits were ok.
Frame, Motor, Tyres.

Due to the age of the system, there was not many troubleshooting documents to be found on the interweb.

I also wanted to run it at 36V, which the stock controller would not be happy with.
Going diy you do loose some of the nice built in features of the controller, unless you buy another with those features.
-Over current protection.
-Regenerative braking.
-Speed regulation
-lots of others
Something with these features is about us$230 landed

The controller was stripped down to see what was inside.

12 years old? Look's like new :)

H-Bridge Mosfets were rated to 60V. P60NE0
There were 2 Driver ICs. ir2104
We will be able to reuse this part of the controller.

The drivers make it much safer on the hobbyist since you can't short the battery by setting the wrong Mosfets on.

There was a voltage regulator onboard (7805) but I could not easily figure out how to turn it on.
And didn't want to risk breaking anything else on the board in case I want to use it later on.

Cut the signal traces to the H-Bridge drivers.
Supply control signals and whola.
Working motor controller.

Bits used
-12v Regulator
LM317, might bump it up to 15v.
Or change for a DC-DC to maximise efficiency.
-Arduino ProMini v2 (Clone, m168)
-Pedals from a computer steering wheel racing set.
-Battery will be a Lithium Polymer (LiPo) pack from Hobbyking.
us$116 landed for a 33.3v(9s) 5.8Ah
Top speed should be 15-20kp/h
At low speed for the kids we should get 30-45 mins runtime.

Currently the program on the Arduino is pretty simple.
Push accelerator pedal to go.
Let go to coast.
Push brake to stop.

To potentially add
Pretty simple in code.
Just need to add a switch.
-Boost button.
Low speed with a 10 second full speed boost available every few minutes.
Make racing interesting.
-Adjustable max speed.
So multiple carts can be set to the same max speed.
During a race it will be driver skill that determines the winner.

Other people have put petrol motors in theirs.
I stayed with electric to keep the noise/maintenance/risk down.
A friend is helping with the metalwork/fabrication side.

Can do a more detailed write up if 3+ GZ members are interested. :)

Samsung galaxy cutdown

, posted: 3-Jan-2013 22:07

Further to my last entry about broken screen.

What is the bare minimum required for it to operate as a wifi network camera?

This much.

Photobucket Photobucket

Well actually a little less.
But I kept the speaker, sim/sd socket on there.
The lower half had the hard buttons, mobile antennas, vibration motor, mic.

How big a heatsink do you need to run a green laser pointer continuously?

, posted: 7-Jul-2012 09:53

At least this big. Ambient 15degrees Celsius.

Purchased from eBay, us$4.61 including shipping.

I need to run them 12 hours at a time, overnight for a project.
Due to the low price these do need a few seconds to warm up.
Once warm they behave as normal.
They start dimming when the case get to 28+ degrees.
Case is diameter 13.75mm. I only have a 13.5mm drill bit so a little pressing with the vice get's it in there.
I could also have scrapped off the rubber black coating for better heat transfer/fit.
Or used a smaller/no heatsink and fan.
Being battery powered why waste energy when you can go passive.
Will also be quieter.

While they many only seem like toys with 5mW of power they are still dangerous due to the concentrated nature of the beam.
Keep away from eyes and planes.

Laptop backlight woes

, posted: 4-Jul-2012 09:46

You know the story, turn the laptop on and screen is dark.
It makes all the right noises.
In order of least to most expensive fix.
Cables - Inverter - CCFL Tube - Screen - Mainboard

In my case I could still see a image with a torch shining on the screen.
It also flickered on briefly at boot.

YNV-18 , HP 8730W
I scoped the pins to make sure it wasn't the mainboard.
7 pin connector.
1+2 , Vcc, either battery or pluged in ac adaptor.
3+4 , Gnd
5,6,7 Didn't note exact allocation at the time,
PWM (for brightness control), Enable Backlight (active high), Enable Light sensor (active high)

The hunt for an inverter began.
A used replacement was located online.
us$14 including shipping.
Even with the fastest shipping it was 4+ days away so went with standard shipping 5-14 days.

On to Trademe for something temporary.
There were a few pin compatible units available.
Purchased one.
Tried a few when I went in to collect.
No go :(
Grabbed a known working one that wasn't pin compatible and tried my luck.

It was also 7 pin.
Wired the 3 control signals to the Enable backlight line.
It works :)
I didn't make the joining cables long enough, otherwise I could have put the cover back on.
No major, just wait for proper one to arive.
I can still close the lid.
Full brightness all the time though.

I also contemplated and upgrade to a LED backlight.
Nearly double the brightness would come in handy during summer outdoors.
Unfortunately they don't hav e a 17" kit.
No eta on one either.
I could have joined two 8.4" kits together.
May still do if I find this too dim outdoors.

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Running a MILWAUKEE M12 Drill from an alternative battery

, posted: 29-Dec-2011 15:53

I needed to replace my aging drill.
Picked up a used 2410-20 from Trademe for $70

Battery from Hobbyking.
nz$15 landed

Soldered some connectors and tested.

No go.
After a bit of reading. the third terminal was for a thermistor.
Phew, I was worried it was a smbus or something fancier.

Soldered a 10k reisitor across the GND and SENs terminal.
Sorted :)

I only used it intermittently so not too fussed with battery life or looks.
Although I could connect a bigger one if required.

Photobucket Photobucket

Cheap logic analyzer review, nz$40 landed

, posted: 26-Aug-2011 08:36

At some point in your electronic hobby you will want one.
Probably after your oscilloscope.

While I did use my scope to do the initial troubleshooting it only had two channels and small window to watch the signals.

After some searching I settled on this unit.

While I could have saved $20 and gotten this
I wanted the probes that came with the more expensive one.
And the warm fuzzy feeling of buffered inputs.

This was my first purchase from via aliexpress.
I would have preferred to use paypal but had to enter my CC details into the site.
My usual point of call is eBay.

8 Days later it was at my door.
No documentation or sw supplied.
After a quick chat to the supplier he sent me a link to download the sw.
It failed to install for some reason so I downloaded the latest version from the original mfg site.
1.1.9 (x64)
Worked fine on Win7 x64.

This unit is a clone of

I have not tested the USBee software as the saleae is doing the job so far.

Connected to project board using SPI at 2mhz, nRF24L01+

So you need sound in your micro project?

, posted: 2-May-2011 22:13

You have a few options.
In the old days (pre 2005?) you didn't have much choice.

If you wanted more than just a buzzer you had to use a sound chip, ChipCorder.
eg ISD2560 would give you a massive 60 seconds at 8khz

A bit of history here

With micros (AVR/Pics etc) now quite powerful you can synthesise speech without too much trouble.

If you need more than 8khz of fidelity, mp3 players were the only to go.
I had worked with mp3 players before by 'pushing' they buttons from a micro to get the desired result.
But this was clumsey.

I had heard of alternate firmware that would allow direct serial control of some players.
Unfortunately with the speed new hardware comes out I didn't fancy my chances there.
A bit of searching located this device.
SD Card MP3 Player Module RS232-TTL

For only us$10, perfect :)
Limited to 199 files only.

I did come across some more expensive ones as well.




So what can a $10 mp3 player do for you?
Loaded some clips onto a sd card and plugged it in.

It does what it says on the box. :)
One thing to bear in mind, there is a small delay, 250ms? haven't measured, between sending the the play command and the clip starting to play.
I am guessing this is the seek time for the sd card.

There is also a pause function.
So you could start then pause.
Restarting is instant.
But the volume seemed to be lower than when you allow the clip to play continuously.
This would be one area a ChipCorder might be useful, faster time to start.

But the convenience of using SD memory for storage far outweighs anything else.

For comparision a 45 second ChipCorder from Jaycar locally. nz$30

The IC markings have been scratched off so I don't know what's under the hood.
Only that it uses a ATMLH044 rom for it's firmware.

Will update once I have used it a bit more.

us$9 Bluetooth Module Review, serial TTL

, posted: 10-Mar-2011 09:11

Also known as BTM5 ,

As found all over the interweb

Got mine from eBay
2x for us$18 shipped.
Preconfigured as a pair

So what don't you get compared to something like
Bluegiga WT32 at us$50

1. It's Class 2, so 10m range
2. Simplified firmware.
This limited it in one particular application where I wanted to scan for devices and show their RSSI.
A kind of digital easter egg hunt.
It has no command to scan for nearby devices.
Or to show RSSI of connection.

3. Might not be found by some devices.
Vodafone 845 found it ok but the Samsung i5700 did not.

4. Bug?
I wired up the slave one to test. Just happened to be the first one I grabbed.
I was configured to 115k.
I could not get into command mode.
After a bit of fiddling I got it.
A. Remotely connect to the device.
B. Disconnect.
C. Pull pin 34(PIO11) high to enter CM.
Pulling it high at power up did not get me into CM.

5. +++ Runs from 2.2-4.2v  Should be able to run straight off a Lithium battery.

So is it worth it?
Definitely if your device can find it :)


Telit GE865 GSM/GPRS Module + Python = Schweet

, posted: 4-Dec-2010 12:33

Just a quick intro and reminder to myself for later.

Not the prettiest setup but it works.
The devboard (ez864) was for an GC864 module, ie one with a connector.
I am only using the regulated PSU and Sim holder on it.
The Sim has not been wired up yet in the picture.


Connected we have
.Serial, TXD, RXD
.RTS, shorted to ground as no flow control is being used.
.ON_OFF, shorted to ground , turns on as soon as power is applied.
.STAT_LED, a good indicator that the moduel is working properly
.GPIO_06, into a led, active high
.GPIO_04, into a switch, active low
.DTR, into a switch, active low. Controls script excution on power up.

The 2.54mm pitch is very generous compared to the 0.5mm on the connector based moduels.
Downside is the lack of an antenna coonnector and fewer GPIO's.
10 vs 22 on the GC864.

While it is not recommended to upload scripts without error checking enabled we will do without for now to save some soldering.

Since Hyperterm is not avaiable for Win 7, I download the successor from the same company.
My usual terminal program, Docklight, did not do file sending.

For a fuller step by step see this link

So, GPS/GSM cat tracker anyone?
Remote montitoring system?

Other links of interest.

Sample code below:--


#A quick intro to Python in relation to running in a Telit Module

# import the built-in modules
import SER    
import MDM
#Internal modem interface

var_response = MDM.send('AT#GPIO=6,1\r', 2)
#Set GPIO6 to output and high.
#Send this AT command to the modem, storing the result code in varible "var_response". ie. 1 or -1
#Same as if you were tying into the modem normally via a terminal program.
#Note this is not the modem response, "OK", but a indication of if the command was actually recieved by the modem
#Reading the modem response is done later in this example.
#For now we will ignore it.
#Note we could also use the inbuilt "GPIO" to work with the pins.

var_response = SER.set_speed('115200')
#Setup the serial port
var_response = SER.send('Type Something')
#Print to the uart
var_response = SER.sendbyte(0x0d)
#Line feed/New line

var_ser_input = SER.receive(100)
#Wait 10 secs for response. 100 x 1/10 secs
#Note the inter character timeout is very short.
#If manually typing it will most likely only catch the first character.
#If you paste into the terminal program it will show the whole string

var_response = SER.send(var_ser_input)
#print what was recieved
var_response = SER.sendbyte(0x0d)
var_response = SER.send('echoed\r')
#Print with line feed

var_response = MDM.send('AT#GPIO=6,0\r', 2)    
#Set GPIO6 to output and low.
#check pin status
var_response = SER.send('Checking pin status\r')
var_response = MDM.send('AT#GPIO=4,2\r', 2)    
#Set GPIO4 to input and read status.
#Internally pulled up by default.

var_ser_input = MDM.receive(10)
#Store modem response, which show the status of the GPIO/Button.
var_response = SER.send(var_ser_input)
var_response = SER.send('EOF\r')

#All this is covered in   Telit_Easy_Script_Python_rXX
#Note all comments are compiled and uploaded to the modue, so take up space.
#Remove them if you want to save some space.
#The GE865 only has 2,013,256 Bytes and this little example is 2,016b

Vodafone 845 Partial Teardown

, posted: 3-Dec-2010 19:11

I was looking for a wired interface into this Android device.

The gps was a logical choice if the serial lines were available.

I figured it was going to be tightly integrated but worth a shot.


Photobucket Photobucket Photobucket

Yup, it was pretty tight in there.

The only identifiable components in there were

1. Vreg. rf3196ms

2. Bluetooth. bts4025

3. WLan. ar6102g-bm2d


The gps may have been hiding under the metal shields but I wasn't game to try and take them off.

I couldn't even find the gps antenna :(

Back to using a Bluetooth serial module.