New, intro, & question

[garumel]

Hellow everyone, I have been reading, and lurking here on this forum for a couple months now, and it is one of the best i have been on.
Now a little background, i am in Iowa USA, 61 years old, started playing with electronics in the late 70s for 3 or 4 years, some tube stuff and transistors, etc. Then 2008 i got back in
again, built some circuits with 555, 4017 and LEDs,and a couple of sound level meters with 3915 chip, and they work fine. I became disabled in 2010 after 2 back surgeries, so late last year i thought about getting in to the micro world to help keep myself busy and sain. After research of Arduino, PIC KIT, PICAXE, ect, i chose PICAXE. So in March i ordered a
20M2 starter kit. I have it blinking 3 different color LEDs. It has been running 8 to 10 hours a day for 5 weeks now, it is awesome. Every so often i will add a few lines of code, and it just keeps going, just simple stuff for now till i learn more as i am an old duffer, old school, slow learner, ect.
Now for the question, i ordered my starter kit from AZTEC MCU.COM, item # B000101. On the web site you can see the setup schematic in the oweners manual (they don't sent it with kit) they use Silcon Labs CP2103 for the downloader and don't use the standard 10k 22k resistors as shown in PICAXE manual, however i included them in my set up and it works fine. I am afraid to use it without them since it does work, But i also know the 20M2 needs at least the 10k to ground. In the future i will make my own board with 12V 2A power supply with 7805 ( for 20M2) and ULN2803 for higher power outputs, and wanted to know if i should use just 10k, or 10k 22k on my board as i don't want to have trouble either way. I am the type i want to know as much about a project as possible before proceeding, helps keep the magic smoke in place. Thanks in advance, sorry for the long post.
Gary

 

[BeanieBots]

Welcome to the forum.
It is strongly advised that you use the download circuit as published by Rev-Ed.
The 10k is ESSENTIAL for correct functioning.
If the serin line is allowed to 'float' you will get erratic effects.
The 22k is required to protect the PICAXE from RS232 voltages which can be ~12v.
If you use 5v logic serial comms then it is not essential but for the sake of a resistor, be safe and fit one.
Please note, the two resistors do NOT form a potential divider. It is a pull down with current limit.
Hope you enjoy playing with PICAXE and please ask if you have any more questions.

 

[kranenborg]

Hi Gary, welcome to the forum as well.

I would suggest to buy just a few simple sensors (thermistors, light-dependent resistors, DS18B20 thermometer, switch) and output devices (LEDS, piezo element, LCD display or maybe even try a small hobby servo) and just proceed with experimenting in the way you have started. The picaxes are very easy to couple with all kinds of sensors and do not need a lot of theory or studying in order to get to the next level. This forum is one of the nicest/kindest available on the net and has a lot of useful info for both real newbies and experienced experimenters. Let us know of your application ideas.

PS, I have made a simple 1-paper summary of the main commands and aspects of the picaxes for those new to the picaxe and microcontroller programming. The sheet refers to the 08M2 but applies almost equally well to the 20M2, maybe it serves you well too: http://www.picaxeforum.co.uk/showthread.php?20337

/Jurjen
http://www.kranenborg.org/electronics

 

[hippy]

It would definitely be recommended to include the 22K and 10K download interface resistors.

Including the 22K and 10K should not interfere with the USB module, allows the PICAXE to work when the module is not connected, and also protects the PICAXE from damage if being powered from batteries or less than 5V.

The manufacturer's boards probably will not include either resistor if it's an 'all on one board' design and the USB interface and PICAXE are powered from the same source. At least the 22K should be fitted if the PICAXE is powered separately ( other than from the USB module ), and the 10K must be fitted if the USB module is to be disconnected from the PICAXE and you want the PICAXE to work reliably when disconnected.

 

[Hemi345]

Since the documentation on that OMS U2P doesn't include a schematic of the actual device, but notes that no external resistors are required and it's "100% compatible", they're probably doing the 10K pulldown and current limit on the U2P. Which means, if you're also adding the 22K current limit and 10K on the breadboard, I think you are creating a potential divider with 22?K on U2P and 10K resistor on your breadboard, then further limiting current with the 22K resistor on your breadboard.

Do you plan to use the U2P to program a PICAXE on your self-made board (just using the gnd, rx and tx)? Some folks on this forum just use a 100K resistor to pull down the SerIn pin when the programmer (similar to your U2P) is disconnected.

 

[garumel]

Thanks for the replys, and the warm welcome. Yes i just want to use gnd, rx, tx for my board, don't want to use usb power. I am wondering about the potential divider as per Hemi345 if my resistors end up in parallel with the cp2103 circuit, then the total resistance to the 20M2 would be half, would that be right? Gary

 

[hippy]

Since the documentation on that OMS U2P doesn't include a schematic of the actual device, but notes that no external resistors are required and it's "100% compatible", they're probably doing the 10K pulldown and current limit on the U2P. Which means, if you're also adding the 22K current limit and 10K on the breadboard, I think you are creating a potential divider with 22?K on U2P and 10K resistor on your breadboard, then further limiting current with the 22K resistor on your breadboard.

The datasjeet seems to have gone off-line at present but I personally wouldn't take any claims of compatibility to mean it includes the download resistors, more that the voltage out was compatible. After all you need the download resistors on the PICAXE side of the circuit to allow it to be removed.

If there is any current limiting resistor on-board then a serial port test and measuring the voltage should reveal that. Reverse engineering the circuit is another option.

 

[lbenson]

Welcome, indeed. I would second kranenborg's suggestion about interfacing to a wide range of sensors. If you search on ebay, a search for "arduino sensor" will come up with many modules which are suitable for interfacing with the picaxe.

I trust you are familiar with the three manuals (see "Manuals" on the menu bar at the top of the forum thread page (the page you are reading)). If you want a thorough grounding in basics from a "newbee" point of view, you could do worse than work through the interfaces in Manual 3.

Basic electronics is well covered at: http://www.kpsec.freeuk.com

There have been several threads which have gone over "parts lists" for newcomers--but I've lost my links to them. Perhaps someone more well-organized will be able to provide references.

 

[Paix]

It looks like the Basic electronics link kindly provided by @Ibenson has moved.

The redirect is to electronicsclub.info.
Presumably the original link with redirection will become invalid in the fullness of time. In the meantime, you can use either!

 

[garumel]

Thanks for the information, i will include both resistors on my board. I do have a good inventory of electronic components of all kinds, and LDRs, buzzers, piezos, RGB LEDs, 7 segment displays,LCDs, ect. as i have been making electronic projects for my grand kids, and myself. I also have several DMMs, a cheaper model DSO oscope, a solder station, and lots of circuit boards- strip boards, and breadboards, pots, stand offs,ect,etc, so i am good in that department. I know i will get a lot of enjoyment from this little chip, and this forum. This fourm is one of the many reasons i chose PICAXE. I am sure i will have more questions later, so thanks again, and i will keep you updated on my progess.
Gary

 

[John West]

Ask any time, Gary. We're here to help each other.

 

[erco]

Gary: Sounds like you're off to a good start. I'm a US PicAxe user as well. I buy my stuff from http://www.phanderson.com/picaxe/

Great prices and lots of useful info. Cheers,

erco

 

[garumel]

Thanks again everyone for your replys, i have read enough of manual # 1, and enough of #3 on interfacing to get me where i am now, but as time allows i will go through them all well, so i can get my head around bytes, words, ect so i can get my 7 segment displays, and LCD going sometime. Thanks erco for the phanderson.com web site, i discovered it after i had ordered my starter kit. I got mine from aztecmcu. It was recomened from a member on (all about circuits) fourm. Thats what got me involved with PICAXE, that it was the easiest way to get in to microcontrollers for noobs like me, as i have no experience at programming. It was very easy to get started, and it looks like it can do a complex program too, so it won't get borring anytime soon. I think it's great and thanks to this fourm i know i made the right choice. Thanks again. Gary

 

[Billo]

With the USB to TTL module that comes with that kit, the 10K resistor should not generally be used if the module is to remain connected to the circuit. The 22K is not necessary either. However, that being said, it can be used with and has been extensively tested with, the normal REV-ED circuit. If you do not ever intend to use regular RS232 serial (via AXE026 or some home-made cable) but do intend to remove the USB to TTL module from your circuit, I would recommend a 50K resistor from serin to ground. That way, when the USB to TTL module is removed, serin is not left floating.

BTW, are you aware that the manual for the kit, and the USB module are available from that site for download?