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Topic: E-Wheelie: Homebrew
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bobbygee 7 posts Popping In	25-08-2009 02:30 Hi All, I have decided to build the project from the ground up using the schematic and firmware available through the Elektor Magazine site as my starting point. I have designed two PCB's; Motor controllers and a separate Logic board. I have had no problem sourcing all of the electronic components in Australia. I have access to two 24V wheelchair motors with associated geerbox (25:1) and 14" wheels which I hope to use. May need to tweek the software to accomodate them. In the schematic published in Elektor, the foot switch is shown with a pull down resistor - should this be a pull up? There is no clear indication in the articles regarding the orientation of the Gyro chip and Acclerometer chip so I have hazarded a guess and may also have to tweek that in software. I will keep you all posted as devlopments occur and I am open to any constructive comments or assistance. Regards - Bob Gilchrist (Brisbane Australia)
Thomas Scherer 1084 posts Power User	25-08-2009 19:10 Maybe this Foto from an original sensor board helps. But take care: this board is hanging like a bat
bobbygee 7 posts Popping In	26-08-2009 01:33 Thank you Thomas, a picture is worth a thousand words. So if I understand you correctly it is mounted upside down under the Controller PCB, no wonder I couldn't see it in the Elektor article. Bob
briany 2 posts Popping In	28-08-2009 12:48 Bob, I am also going down the homebrew route but am not quite as far advanced as you. I managed to figure out from the picture on the front of the July / August magazine which way round the sensors go (you can see the "pin one" identifiers for both chips and enough of the board to work out which way it goes!) I think the right orientation is that the Y axis is across the board (side to side) and X is front to back. The sensor daughterboard sits on top of the bottom left of the main board which itself is upside down (like a bat as Thomas says!) so it's been rotated around the X axis so that the Y axis is reversed. For what it's worth you can buy both sensors already fitted to breakout boards (made by Sparkfun I think) which are 0.7 inches square which makes soldering these components a lot easier - some of the resistors and capacitors on the boards are different values - I have changed them although I suspect they probably still work and it is a bit fiddly to resolder the 0603 size SMD devices. I found a source in China for the 1020Z motors so once these arrive I should be able to put it together. For wheels I'm using electric scooter wheels which came with tyres and tubes for less than £10. I've cut the hubs down to hake the hub thickness much less and these should attach directly to the motor shaft. Brian
bobbygee 7 posts Popping In	02-09-2009 05:43 I got a little confused re the sensor orientation because the original (prototype?) article shows the control board mounted on the base of the unit normal way up but the final aricle shows it mounted upside down under the cover. Not sure if there is a difference in the firmware to accomodate the change but I guess it will be easy enough to tweek. I have sourced some surplus 450Watt 24Volt 550RPM motors from Oatley Electronics in Australia for $129.00 AUD each which I think will be closer to the design criteria than the wheelchair motors that I already had. Thank you Brian for the heads up regarding the chips on carrier boards, Sparkfun is a very interesting site, where have they been all my life? I am currently analysing the firmware and note that there are some diagnostic LED sequences, is there a list available with inerpretations. My next step is to sloder the SMD's to my board - a new experience for me but there have been some excellent articles in Elektor recently so confidence is high! Bob
Gamri 1 post Popping In	02-09-2009 12:01 how did you find the parts list. i mean ok by reading the circ diagram but for eg the wattage of the resistors, the voltage of the capacitors? thanks and well done
Thomas Scherer 1084 posts Power User	02-09-2009 16:55 @bobbygee please note that the firmware as released by Elektor is preliminary. So you still have to wait a little for the "GM". In a few weeks' time, have a look at the German Elektor forum, because heavy optimizing will occur (I believe) and the source comment will normally be in English. @Gamri wattage is standard (0.25W) - only R16 is preferably 2W. And voltage: unless otherwise noted, standard Cs are rated 60V. Post edited by Elektor Editor on 03-09-2009 11:24
bobbygee 7 posts Popping In	03-09-2009 04:29 All of the PCB components with the exception of the IDG-300 are available from Farnell Electronics. The IDG-300 is available from the manufacturer, Invensense, directly. I have seperated the motor controllers from the main logic PCB because I have other applications that they will do nicely for - so there is a controller PC Board for each wheel. The main consideration with respect to the Wheelie design is the Current sense IC which I have included on both motor drive boards and I will modify the ATTiny25 firmware to read the extra current signal on a spare ADC channel. Regards Bob
Thomas Scherer 1084 posts Power User	03-09-2009 11:52 should be no problem. The firmware for the tiny25 is so simple - just do it
briany 2 posts Popping In	27-09-2009 22:01 I have finally got to the stage where I am about to program the AVRs, having got the motor controllers and the sensors working. The firmware available states the fuse bits needed for the ATTiny but not the AtMega - can someone confirm what these should be - I assume the most critical element is setting the 16MHz crystal as the clock, and probably none of the other settings really make a difference, but it would be good to be sure!
HK-Willem 1 post Popping In	01-11-2009 12:28 Hi All, I have also decided to build from scratch. I have a interesting question. If I want to use a TQFP Atmel ATMega32 will the Hex files worked as is or will it be needed to re-compile for the new physical footprint? Willem
guenter 1087 posts Power User	01-11-2009 20:59 Hello Willem, the TQFP is no Problem. My Wheelie has an TQFP: http://www.gerold-online.de/cms/en/wheelie/mein-wheelie.html
Thomas Scherer 1084 posts Power User	18-11-2009 00:21 @HK-Willem Have a look on this screenshot made from AVR-Studio 4 Post edited by Thomas Scherer on 18-11-2009 00:23
edjacob 4 posts Popping In	29-11-2009 16:15 Hello, I´m starting to build this stuff but I could´t find the original sensors, IDG300 and ADXL 320, so I got a finished board with IDG500 and ADXL335, from sparfun. Do you think that I have to tweak the software to have a good performance with these sensors ? Thanks
Thomas Scherer 1084 posts Power User	01-12-2009 20:44 IDG500 should be totally equal if you set it to "500°/s full scale range (higher speed)" For using the ADXL335 instead of ADXL320 you should better match the gain difference in the firmware for the 335 delivers 300mV/g vs. the 320 with its 175mV/g. With other words: your replacement is more sensitiv. Maybe it would be easy to have a look in the newest open firmware in the german forum because this code is simpler to read an modify: http://www.elektor.de/forum/foren-ubersicht/foren-zu-elektor-projekten/elektorwheelie/elektor-wheelie-open-firmware.1131470.lynkx?pageStart=11 But see the latest versions attached here for your conveniance: EWOF101.bas EWOF101.hex Post edited by Thomas Scherer on 01-12-2009 20:45
bobbygee 7 posts Popping In	16-01-2010 02:21 Well I'm back after an extended period of unemployment (therefore limited cash) and dubious health. I am currently debugging my PCB designs and particularly the sensor area as I am very new to surface mount and I find I am battling that at the moment. I have attached some pictures of the PCboards I have made. Hope to move on to mechanical assembly shortly.
guenter 1087 posts Power User	20-01-2010 18:11 Super PCB!! How did you make the vias? Günter
bobbygee 7 posts Popping In	30-01-2010 12:15 Hi Gunter, I use 'Express PCB' software to design my boards and then submit them by email to be manufactured ... presto in 5 working days these beautifully manufactured PCB's arrive from the USA. http://www.expresspcb.com These boards are all 2 layer (although it is possible to do 4 layer boards) and all component holes are vias (I overlay a via hole onto smd pads). I use a groundplane on the top as ground and another one (sometimes more than one) on the bottom for + supplies. The boards I use are a special 'Miniboard' prototyping service and are manufactured in quantities of 3 (2.5"x3.8") boards for around US$51.00 plus postage. I have used this service for years and find that even my dodgiest prototypes look and perform great. Regards Bob
bobbygee 7 posts Popping In	01-02-2010 09:26 Finally got my prototype set up in a test jig, now have to source another battery as one of these is faulty.
mcgillg 1 post Popping In	15-12-2010 21:11 Bobbygee: Would it be possible for you to share your Expresspcb file? It would save me a whole lot of time. Kind Regards