Help with reviewing my components list before i buy them.

[Guitar-FL]

Hello from Australia Megadrum forum members, any other members from Aussie?
Anyways i wanna build Megadrum for the drummer in my band so we can jam occasionally in my room with a electronic drum kit. Disclaimer: Im a complete noob with electronic components.

Ive compiled a list of all the components ill be buying and just wanted Megadrum members to review it before i buy the parts just in case im buying the wrong component.

The list is in the same order as in the documentation page here http://www.megadrum.info/content/buying-components and is labeled for easy viewing.
Most item will be purchased from http://www.futurlec.com.au/ they sell components really cheap no minimum order quantity. If you want to personally check the items out just punch in the product code on the website.
I was originally going to buy the parts from Farnell Australia but what really annoyed me was the minimum order quantity for some of the items were sometimes 10 or maybe 25 when i only needed 1.

I have just a couple of questions which are confusing me, all help will be much appreciated.

Some of the components like the capacitors in Farnell like the 22pf says 200v in the description whereas where in Futurlec its says 50v, now im assuming its the maximum voltage rating or something it can withstand am i right? or wrong

I will to buy the ICs from Farnell. When i was looking at the
STMICROELECTRONICS M74HC4051B1R IC, LOGIC, 74HC, MULTIPLEXER it was Out of Stock but the exact replacement was http://au.farnell.com/nxp/74hc4051n/74hc-cmos-74hc4051-dip16-5v/dp/380910
The only difference i could find was that the "On State Resistance" was 80ohm whereas the M74HC4051B1R had a "On State Resistance" of 50ohm. Does this matter?

Searching the Futurlec store didnt come up with a 470nf resistor but it came up with 0.47uf which im guessing is the same thing because when i searched up 100nf it came up with 0.10uf (100nf) resistor.

Ok one more question i promise

The 6.35 inputs from Futurlec had 2 variations "SWITCHED" and "UNSWITCHED" the unswitched was like 1 dollar cheaper so i went with that. Did i chose the wrong one?

If someone could review my components list and give me a "OK" itll be much appreciated.

Thanks

[Firelord]

Disclaimer: Im a complete noob with electronic components.

Maybe you should consider getting a Synthex kit then? If you have little experience in electronics then you might run into problems during assembly of MD. The kit makes this process easy though.

[Guitar-FL]

Ive considered getting the kit but i like making things from scratch, i don't know i guess its more fun for me and a good learning process.

[jman 31]

You can use a standard 1/4 watt carbon resistor and save a bunch of money. The metal film resistors may be necessary for audio quality, but are not going to improve anything here. That's just my opinion, but I'm sure others will agree.

[Firelord]

Ive considered getting the kit but i like making things from scratch, i don't know i guess its more fun for me and a good learning process.

All right then.

now im assuming its the maximum voltage rating or something it can withstand am i right?

You are right. It is the maximum voltage rating. MegaDrum works at lower voltage levels (+5V), so a cap with a voltage rating of 25V should be fine.

470nf resistor but it came up with 0.47uf

1uF = 1000nF, so the math for this one is easy, right?

The only difference i could find was that the "On State Resistance" was 80ohm whereas the M74HC4051B1R had a "On State Resistance" of 50ohm. Does this matter?

I don't think so.

The 6.35 inputs from Futurlec had 2 variations "SWITCHED" and "UNSWITCHED"

The difference here is that switched inputs can be used as an additional switch for turning something on/off (e.g. in a portable CD recorder application: if you plug in the headphones, the loudspeaker(s) will be automatically turned off). MD does not use this functionality so there is nothing wrong with the unswitched jack.

Now, as for the component list in general: please make a revision, because you are definitely missing some components. These are in the component list PDF that comes with the design (see the latest schematics topic).

OTHER IMPORTANT NOTES:

- You need a 20MHz crystal for ATMega324P (16MHz is for ATMega32);
- The 1uF tantulum cap is under question, I think it should be OK, but it has polarity so be careful, in the design the 1uF cap doesn't have polarity.
- If I remember correctly you need at least 5 1N4148 diodes;
- BAT42 is NO GOOD! You need BAT85's.

[Firelord]

More notes on the list:

- Make sure that the socket for the PIC (ICS28 in your list) is a narrow one (i.e. compare the PIC and socket dimensions via Data Sheets);
- The 4-, 5- and 6- pin header connectors are useless without corresponding terminals (to which wires are squeezed or soldered and inserted into the connectors afterwards);
- Also make sure you have the necessary tools for the job, e.g. a good soldering iron (preferably with tip temperature regulator), pliers etc;
- You need a flat ribbon cable of 40 wires and 16 wires (about 0.5m length for 40x and 1m for 16x, or you can get a single 40x cable and cut it in two for 16x, it's up to you).

[Guitar-FL]

One thing im also confused about is getting the right Amtel chip
there are so many variations, which is the better, the Atmega32, Atmega324P, Atmega 644, and then the frequency clocks 16mhz and 20mhz. so confusing
I had a look at the latest components list in the pdf for

29/01/2009
Updated Digital board for future 40/48/56 inputs.

, this is confusing me aswell, there are parts there that arent in my list but there are parts in my list that arent on this pdf.
what is the CN1, CN2 etc...? P1, P2?

You need a 20MHz crystal for ATMega324P (16MHz is for ATMega32);

The list says Atmega32-P and the crystals at the bottom of the list are 16mhz and 12mhz

If I remember correctly you need at least 5 1N4148 diodes

The list only has it written once

[Firelord]

The thing is that the list is OUTDATED. Dmitri suggests checking the latest schematics for a complete list. And I suggest you give it some time before ordering anything; get a clear picture of what you really need. We're here to help

I understand how it all must be confusing because I've been there myself — I ordered the components following the list on the site and when I got them it turned out that I either needed more components (some resistors for the digital board) or found some parts in the schematics different from those I ordered (like in the case of 20MHz crystal which is required for ATMega324P). It was really frustrating. But it serves me right — I should have spent more time reading the documentation and schematics.

there are so many variations, which is the better, the Atmega32, Atmega324P, Atmega 644, and then the frequency clocks 16mhz and 20mhz

I suggest getting ATMega644 if it is possible, it can run off a 20 -or- 24 MHz crystal (I'd suggest getting the 24MHz crystal). With ATMega644 you can have more inputs if you decide that you need it in the future.

CN1, CN2 etc...? P1, P2?

These are various connectors. I think you have them on your list.

All right, one more IMPORTANT thing to mention.

You can save yourself a LOT of pain in terms of drilling and soldering, if you are able to find 4851 multiplexers INSTEAD of 4051. THEN you DON'T have to order 64 BAT85's and you'll need LESS 100R resistors (-32 from your list). Then, when assembling MD, you replace the 32 100R resistors with jumpers, and you do not have to drill holes/solder in the BAT85's.

[Guitar-FL]

Thanks Firelord you cleared alot of things up.

You can save yourself a LOT of pain in terms of drilling and soldering, if you are able to find 4851 multiplexers INSTEAD of 4051

I couldnt find the 4851 multiplexers.
When i looked through the latest components list the multiplexers weren't even listed there. Is the new list showing a new revision of Megadrum?
like a new streamlined version or something?
I think the only thing thats taking me back and forth is what i need to buy. The build will be quite simple and easy to follow. Im a beginner with"components" but i have done DIYS on electronics before.

[Firelord]

I couldnt find the 4851 multiplexers.
When i looked through the latest components list the multiplexers weren't even listed there.

The 4051's are listed in the analogue board - components list.pdf. If you are unable to find the 4851 then you'll have to stick to 4051 + 64x BAT85's and the rest of the 100R resistors.

The thing is that Dmitri probably doesn't have time to keep the component lists in sync with every design update.

I think the only thing thats taking me back and forth is what i need to buy. The build will be quite simple and easy to follow. Im a beginner with"components" but i have done DIYS on electronics before.

Ok, well getting the right components is rather important (especially if you are only able to order parts).