# Cheapo MP3 player update



## Otaku (Dec 3, 2004)

Hi all,
I worked out the timer circuit for turning the player on remotely. It can be activated with any dry contact switch (mat, PIR, manual switch etc) as long as no voltage goes to the player. I'll have the circuit for turning it off in a another week or so. I'm getting the circuit drawings done as I go, and will include pics. The first timing circuit looks a bit sloppy - a couple of false starts, and I'm not the best at circuit board layouts. Progress is being made! More to come...


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## Frighteners Entertainment (Jan 24, 2006)

What cheapo unit are you using?


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## Otaku (Dec 3, 2004)

This one:
http://www.mpja.com/category/Unique_Items/MP3_PLAYER_16520_MI.asp

For $5 it's a pretty good deal, but you have to buy three of them to meet the minimum order.


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## Frighteners Entertainment (Jan 24, 2006)

yeapers, good deal!


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## Brad Green (Jul 29, 2004)

Otaku; As you know from my various pleas for help, I've been playing with one of these units, and I noticed that once recorded, they will play a constant loop. Will your "OFF" circuit have the ability to 'time' the play event? Just curious because I'm trying to run Stephen Lynch's "Halloween" through a Scary Terry setup and have'nt quite figured out how to stop at the song's end rather than have it immediately start to play again.


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## Otaku (Dec 3, 2004)

In a way. Right now, I'm planning to use a second timer circuit to control the power to the player. Both timers will start at the same time, but one stops after starting the player (~1.5 sec). The other timer stays on for the duration of the file, and will be controlled by a potentiometer. This means that you need to know the length of the file, and you'd need to play with the timer a bit to "dial in" the pot. Adding a short silence period at the end of the file will help in preventing restarts. I'm still trying to determine a way to monitor the playback IC so that it can be shut down at the end of the file, but can't find any info on the chip. I suspect that it has proprietary firmware in it as well.


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## Otaku (Dec 3, 2004)

Whew! OK, I built and tested a 556 timer circuit that lets me turn on the MP3 player, play the file once, and shut down the power supply to the player when the file is finished playing. The next trigger event starts the whole thing over again. This circuit is pretty much a prototype, so is a bit messy. I also plan to use a different board (easier to use) for the next builds, so I'll start the how-to picture fest when I get the new parts. The bottom line is that one can now turn these players on and off remotely, with the event controller of your choice.


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## bourno (Jan 21, 2006)

I take it, these have good sound quality? I was thinking about getting some cowlacious recorders at some time, but if these are nice....

Adding a couple more relays to one of my prop controllers wouldn't be a big deal. What do you guys use for amplified speakers? I was checking out Radio Shack's MP3 portable speaker for $5.97. Their item # 10-1469


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## Otaku (Dec 3, 2004)

These players have very good sound quality, and you get the bonus of stereo tracks. The ISD chips in the Scary Terry boards can only record mono. They hold several minutes of sound, depending on the bitrate used in the file (Dennis at Wolfstone estimates that at certain rates, the player will hold ~30 mins). For $5 each they're hard to beat, especially if you're planning a looping soundtrack.


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## slimy (Jul 12, 2006)

We love Otaku!

Now, get that how to up.


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## Brad Green (Jul 29, 2004)

They seem to play well on just about any decent set of amplified computer speakers Bourno, I'm using one on a Scary Terry skull with a split track and had to modify a set of speakers into an amplified mono-setup and it turned out well. You will be really surprised how well these little mp3's record and play! And yes, we love Otaku!


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## Zombie-F (Apr 12, 2004)

Yeah thanks Otaku. You've just given me the power of great sound quality at even lower cost than a chipcorder.


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## Otaku (Dec 3, 2004)

It'll take a couple of weeks to get a good how-to together for this hack. I'm still in the R&D stage, and am looking for the best board to make the timer assembly easy. The concept is proven, however, and I just need a solid parts list. I'm trying to single-source all the parts. I have the circuit drawing, but its in a .doc format so I can't attach it to a post. If anyone wants a copy, PM me and I'll email to you. Please note that I may be changing the values of the 470 uF cap and the 1 MOhm pot - I'm still experimenting with this part.


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## Otaku (Dec 3, 2004)

OK, I have the circuit worked out. The values of the 1 Meg potentiometer, the 1K resistor and the 470 uF cap can be varied to change the timing period. I'm still working out the how-to, but here's a drawing of the circuit. The remainder of the circuit that connects the relays to the USB connector and the MP3 play button are in the works and I'll post it soon.


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## ScareFX (Aug 18, 2004)

Thanks Otaku. This looks like it will be a "must do" project.


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## gmacted (Jan 18, 2006)

Otaku said:


> OK, I have the circuit worked out. The values of the 1 Meg potentiometer, the 1K resistor and the 470 uF cap can be varied to change the timing period. I'm still working out the how-to, but here's a drawing of the circuit. The remainder of the circuit that connects the relays to the USB connector and the MP3 play button are in the works and I'll post it soon.


Otaku,

Before I make any suggestions, i just want to say I think what your doing is great! I don't want to come off as negative, but I have a few questions and suggestions for your circuit.

I am questioning why you have output pin 9 "sinking current" and output pin 5 "sourcing" current. Please keep in mind that the 555/556 can only sink/source up to 200mA of current when choosing your relay. The ouput pins will only go so "low" depending on how much current you "sink". It would probably be better to "source" the current in both cases.

In any case, the "sorcing" output pins will need some additional diodes. Since the relay coil is "inductive" you should place a rectifying diode (1N4001) in series with the output pin and the coil to ensure that a small 'glitch' cannot be fed back into the IC. Without this extra diode monostable circuits may re-trigger themselves as the coil is switched off. Also, a standard protection diode (1N4148) should be connected "backwards" across the the relay coil.

These additions to your circuit will avoid false triggers and preserve the life of the 556 timer.

I think I may try this myself. I can't wait for the how-to! Thanks again.


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## Otaku (Dec 3, 2004)

gmacted,
Thanks for the suggestions. I had seen the use of the diodes on some circuit drawings, and was thinking about doing that myself. As regards pins 5 & 9, the wiring is as found on several circuit examples I looked up on the web. I am paying attention to the current requirements of the relays I'm choosing, and will keep the coil current demand low (< 100 mA). More to come...


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## gmacted (Jan 18, 2006)

Otaku said:


> gmacted,
> Thanks for the suggestions. I had seen the use of the diodes on some circuit drawings, and was thinking about doing that myself. As regards pins 5 & 9, the wiring is as found on several circuit examples I looked up on the web. I am paying attention to the current requirements of the relays I'm choosing, and will keep the coil current demand low (< 100 mA). More to come...


Please keep in mind that the more current that you sink, the less close the output pin will go to a low (or 0V). When sinking 10 mA, the ouput will go down to 0.1V. When sinking 100 mA, the output will only go down to 1V. They relay should still engage, but just keep that in mind. The 555/556 is much more stable when sourcing current.

Keep up the good work!


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## Otaku (Dec 3, 2004)

Here's the latest revision of the timer circuit. I still have to draw the power connections to the USB connector and the player start button wiring. Many thanks to gmacted for his valuable advice on the addition of protection diodes. I'll try to get a pic of the start button wiring up later today.


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## gmacted (Jan 18, 2006)

Otaku said:


> Here's the latest revision of the timer circuit. I still have to draw the power connections to the USB connector and the player start button wiring. Many thanks to gmacted for his valuable advice on the addition of protection diodes. I'll try to get a pic of the start button wiring up later today.


Looks good Otaku. One little mistake I noticed. You have the 1N4001 diode for the bottom relay incorrect. It should be connected to pin 5. The whole purpose of the diode is to protect the IC.

Everyone better hurry up and buy those MP3 players! With this how-to they may sell like hotcakes!


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## Otaku (Dec 3, 2004)

Thanks, gmacted. I fixed the error in this drawing. Please note the solder locations on the MP3 module's play button - I found these to work for starting the player, but they're very small surface-mount pads. Use a small solder tip and 30 gauge wire. I plan to use a 2-pin Molex connector to attach these wires to the circuit board. You need to be able to disconnect it to upload files.


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## Otaku (Dec 3, 2004)

Oooops! The software dropped a line where it didn't belong - here's the corrected version. Note: the MP3 player is shown with the case opened.


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## gmacted (Jan 18, 2006)

Otaku said:


> Thanks, gmacted. I fixed the error in this drawing. Please note the solder locations on the MP3 module's play button - I found these to work for starting the player, but they're very small surface-mount pads. Use a small solder tip and 30 gauge wire. I plan to use a 2-pin Molex connector to attach these wires to the circuit board. You need to be able to disconnect it to upload files.


Very nice indeed!


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## Otaku (Dec 3, 2004)

I've almost finished the parts list for the circuit. Almost everything you need is at All Electronics. The hardest part to get is the USB-A female connector. Jameco has them (p/n 161023, 0.79 ea.), but you get stuck for shipping one part. What I did was to request free samples from Keystone Electronics.
http://www.keyelco.com/products/specs/spec141.asp
Click on the sample link and make up some info about your "company" and how many you plan to buy each year (at least 1000), and they'll send them to you for free. I got 10 of them, but they did email me saying that this was more than they usually send for sampling. Try for 4-5 and you'll be OK.
I want to post a decent how-to for the assembly of the board, so it's going to take a little while. I want to get lots of pics as I go along.


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## Otaku (Dec 3, 2004)

*Circuit map*

I made a layout drawing of the circuit to make it easier to see where everything goes. It's based on a PC-3 board available from All Electronics. All questions and feedback are welcome!


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## bourno (Jan 21, 2006)

I haven't gotten mine yet, but why do you need a female USB connector? Is there not an easy way to just break the power of the battery in the battery part of the player by adding an insulator there and use the relay to remake the connection?

Maybe it will make sense when I get mine from MPJA


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## Otaku (Dec 3, 2004)

Actually, I did think about doing it that way. You could tap into the battery terminals in the case and wire Relay A to control the power, it just needs another Molex or similar connector. I just liked the ease of plugging the MP3 module into the board.


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## Otaku (Dec 3, 2004)

I'm expecting the parts for this hack to arrive next week, at which time I'll start the how-to. There's going to be lots of pictures and text, and trying to post these will run me out of attachment space real quick. Is anyone interested in hosting the how-to on their web site?


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## bourno (Jan 21, 2006)

Not a problem for me to help you out on that. I am sure more will volunteer as well


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## Otaku (Dec 3, 2004)

Thanks, bourno! Let me know what formats you'd need for the pix and text instructions and how to get them to you - the parts are on the way.


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## heresjohnny (Feb 15, 2006)

I can help too if you need it.


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## ruafraid (Jan 3, 2006)

Do we have a "Final" Diagram / Schematic this thing has changed a few times which is expected. I started to build it and stopped when it changed a whole lot. So I am trying to get back in sync.


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## Otaku (Dec 3, 2004)

Yes, the final circuit layout is on my post dated 1/19/07. I don't know how to link to a thread or post.


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## Otaku (Dec 3, 2004)

For those who will be building this circuit, go to R/S and get a spool of bus wire:
http://www.radioshack.com/product/i...&cp=2032058.2032227.2032239&parentPage=family
It will make the bus bar layouts way easier, as you won't need to strip wire.

I'm putting the first board together and taking pix as I go. After I finish the first one and test it, I'll post a parts list. More to come...


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## bourno (Jan 21, 2006)

jpg pics would be best for me. I will just copy and paste in the text from either the e-mail itself or if you wanted to microsoft word, that would be fine too.

Send them to bourno (at) teambac.com

I will just add a "Otaku MP3 player hack" to my project page list. I just got back from a work trip and gonna have to make some time to see what addition hacks could be done to the player.


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## bourno (Jan 21, 2006)

I have thrown together a small how-to for using it with a Prop-1 or similar type controller board. I haven't soldered anything up yet, but did the testing by manually jumping the connections at this time.

http://www.teambac.com/web_hall/MP3_player_hack.html


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## Otaku (Dec 3, 2004)

Looks good, bourno! Is the Prop-1 able to detect the end of the MP3 file to prevent replays? That's the biggest hurdle I ran into - nobody seems to be able to find any info on the player's controller chip. I did find a datasheet on the MP3 decoding chip, but none of the output pins had anything useful for detecting end-of-file.


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## Zombie-F (Apr 12, 2004)

Otaku said:


> Looks good, bourno! Is the Prop-1 able to detect the end of the MP3 file to prevent replays? That's the biggest hurdle I ran into - nobody seems to be able to find any info on the player's controller chip. I did find a datasheet on the MP3 decoding chip, but none of the output pins had anything useful for detecting end-of-file.


But if you know the length of the sound file being used, couldn't you program a pause into the prop-1 and then have the prop-1 stop the playback before a replay occurs? Of course, you'd need to change this pause time based on the length of your sound files, which means changing it any time you use a new sound file.


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## bourno (Jan 21, 2006)

It would be like yours Otaku for needing to time it out for pulsing the play/stop button again as Zombie mentioned.

It is just too bad there isn't any easy way to make it behave like we want instead of needing a controller that could be more expensive than the MP3 player  But, if a person was already using a prop-1 or similar on the prop already, it would be a wash then


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## Otaku (Dec 3, 2004)

The pause between replays is ~ 0.5 sec, according to my 'scope. Of course, if one adds a few secs of silence at the end of the file, it gets easier to hit that target. True, you would have to recode the pause or relay-off for each change in the file length. The 556 circuit allows setting time periods on the fly.


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## Otaku (Dec 3, 2004)

bourno said:


> It is just too bad there isn't any easy way to make it behave like we want instead of needing a controller that could be more expensive than the MP3 player  But, if a person was already using a prop-1 or similar on the prop already, it would be a wash then


I hear ya. I'm not giving up on the controller chip, though. If I can find the right info, I'll re-design.


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## Otaku (Dec 3, 2004)

Another oops! I re-checked the timing calc's and found that the 1 MOhm resistor should be a 100K. This is part E on the circuit drawing. Apologies for the mix-up. The minimum playing time will be ~24 secs, max time ~4.4 minutes.


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## Otaku (Dec 3, 2004)

A quick update:
The circuit design is verified. I'm changing one of the relays (the DPDT) to a 6VDC to handle any voltage dips that a low battery might deliver. The current 12VDC relay only works reliably with a 12VDC power supply, and I want this thing to be completely stand-alone. I have lots of pix for the how-to and am compling it a little each day. Cropping pics sure can take a lot of time. Thanks for your patience, and for the valuable input and critiques of this project. I'll get the parts list up after I install the 6VDC relay in the test board and confirm functionality.


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## heresjohnny (Feb 15, 2006)

Thanks for all your effort with this Otaku, these things seem to always take a few revisions before they are right.


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## Otaku (Dec 3, 2004)

I tested the 6VDC DPDT relay today and everything works on a 9 volt battery. Many thanks to gmacted for pointing out the correct direction for the diodes. I'll be out of town for a few days, but I will get a complete parts list up next week. A note of caution: do not get the polarity reversed. I did that today and immediately blew a hole in the 556 chip.
For some reason I can't upload an attachment here. I'll try to post the circuit layout to Halloween Gallery.

Nope, still having problems with Halloween Gallery uploads, too. If anyone wants to see the latest revision, drop me a PM and I'll email the pic.


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## Otaku (Dec 3, 2004)

I've had some requests for the final circuit layout for this project. I posted the pic on Halloween Gallery:
http://halloweengallery.com/displayimage.php?pos=-3678
Let me know if you have questions. Again, mucho thanks to gmacted for the help on the fine-tuning of this circuit!


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## gmacted (Jan 18, 2006)

Otaku said:


> I've had some requests for the final circuit layout for this project. I posted the pic on Halloween Gallery:
> http://halloweengallery.com/displayimage.php?pos=-3678
> Let me know if you have questions. Again, mucho thanks to gmacted for the help on the fine-tuning of this circuit!


You deserve all the credit here Otaku for the great idea! I'm just glad I could help a fellow Hauntforum member.


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## Otaku (Dec 3, 2004)

Here's the parts list for the project. Some items, like resistors and diodes, have minimum quantities that you have to buy, but they're the really cheap parts. I didn't include the cost of wire since we all have some of that lying about, nor the cost of the USB-A sockets.
The how-to is coming along, but my schedule has been pretty crazy lately so it's taking longer than expected. Thanks for your patience.
Here's the link to the parts list:
http://halloweengallery.com/displayimage.php?pos=-3679

As some of you have probably guessed, some of the parts are optional. You can use any enclosure or box you want to, and wire nuts can be substituted for the 1/8" jacks and plugs for connection to the controller and MP3 player trigger wires. The cost seemed pretty high to me after I totaled it up, so some of these subs will reduce the price.


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## Otaku (Dec 3, 2004)

I posted some pix of the completed board today. I'm still learning Adobe Elements 5.0 so it's taking a lot longer for me to be able to edit pix and insert text boxes etc.
http://halloweengallery.com/displayimage.php?pos=-3680
http://halloweengallery.com/displayimage.php?pos=-3683
http://halloweengallery.com/displayimage.php?pos=-3682
http://halloweengallery.com/displayimage.php?pos=-3681

More to come...


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## Otaku (Dec 3, 2004)

I have a PDF of the instructions for wiring the IC into the board. I'm still working on the pix for attaching the pot, relays etc, but this part of the assembly is the most difficult. It's too large (737KB) to upload to Halloween Gallery, so if anyone would like to get a copy or post it on a web site, PM me and I'll send it along! Thanks again for your patience.


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## kruella (Feb 23, 2007)

Otaku,

I wanted to thank you for posting the cheapo mp3 player link. I purchased 2 for my talking skulls and I'm thrilled with them! 
They work great!!!


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## bourno (Jan 21, 2006)

I have posted Otaku's PDF on my web site along with the the parts list and schematic drawing.

Otaku's MP3 hack
.
.
.


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## Otaku (Dec 3, 2004)

I just noticed that the 6VDC DPDT relay (RLY-468) at All Electrtonics has been sold out. You can substitute the RLY-642 relay for this component on the timer board.


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## bourno (Jan 21, 2006)

I have uploaded Part 2 of Otaku's circuit onto the the link from earlier.



bourno said:


> I have posted Otaku's PDF on my web site along with the the parts list and schematic drawing.
> 
> Otaku's MP3 hack
> .
> ...


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## Otaku (Dec 3, 2004)

A quick note - I built a third timer board this week and found that the 1.0 uF cap/1.5 Mohm resistor combination did not allow enough time to trigger the player. I added a 100K resistor to the 1.5 MOhm in series and that fixed the problem. I'll include a pic in the last part of the how-to that shows how to cut in the 100K resistor. This was likely caused by variance in the cap - tantalum caps have ~5% tolerance.


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## Otaku (Dec 3, 2004)

Just curious - has anyone tried building this timer yet? If so, would you let me get your feedback as to the accuracy of the layout drawing. Also, does the how-to cover everything OK, at least up to this point? Thanks!


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## gmacted (Jan 18, 2006)

Otaku said:


> Just curious - has anyone tried building this timer yet? If so, would you let me get your feedback as to the accuracy of the layout drawing. Also, does the how-to cover everything OK, at least up to this point? Thanks!


I plan on building one or two of these. Everything looks good to me, but I may not be the best person to ask because I know how the circuit works.


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## Otaku (Dec 3, 2004)

Yeah, Greg, I was more interested in the feedback from folks that don't work with this stuff regularly. I tried to plug in as much detail as needed without being too overbearing - hopefully I didn't miss anything critical.


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## Otaku (Dec 3, 2004)

I've completed one of the MP3 timer systems, and will (hopefully) be able to enter it in the $20 Prop Contest. Yeah, I know it's not really a prop, but these devices will sure improve my sound effect capabilities. I should have Part 3 of the how-to finished by next week. Thanks, everyone, for your patience.

Later - Just heard back from Z-F, he says no problem entering it for the Prop Contest! Thanks, Z-F!


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## Otaku (Dec 3, 2004)

I finished building out one of these last night, and I've been playing with it this morning. Setting the "on time" period is quick and easy - it takes me 2-3 tries. I'm adding a 5 sec. silence period to the ends of the test files so I don't have to be exact with the setting. The timing appears to be very stable and repeatable.
Something I've noticed with these players: I tried using one with my talking Reaper, and found that the low output voltage level of the player doesn't work very well with the servo driver board I have. It's an older AutoTalk board from BPE, and I think they designed around the 2.5 volt output of the ISD chips. I'll either have to add a small pre-amp or change to a different servo board.
Has anyone used these players with a Scary Terry board? Carl at Cowlacious said the S-T boards can handle fairly low input voltages, but wasn't sure about the behavior with these players.


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## Brad Green (Jul 29, 2004)

The little mp3's work great with the Scary Terry board. It's what I'm using to drive the one I built, and it operates the servo smooth as glass!


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## Otaku (Dec 3, 2004)

Most cool! Thanks, Brad, I was hoping that they would work. I'll pass this along to Carl and place an order for a board.


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## Otaku (Dec 3, 2004)

Update - Part 3 of the how-to is done! Let me know if any questions arise.


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## GraveDiggerGreg (Nov 12, 2006)

OH NO.... is www.mpja.com GONE? I get a error message saying website does not exist! - hope someone has a second source


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## ScareFX (Aug 18, 2004)

GraveDiggerGreg said:


> OH NO.... is www.mpja.com GONE? I get a error message saying website does not exist! - hope someone has a second source


Still there for me...maybe their server was down?


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## GraveDiggerGreg (Nov 12, 2006)

You are correct.. they are back up - some of the pages are not responding such as contact us, but seems that they are back. thanks


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## TwistedDementia (May 2, 2007)

Thank's for posting the cheapo mp3 player link. I just purchased 5 for various project's including this one.


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## Devils Chariot (May 23, 2007)

*Ressurection!*

Hey thought I'd ressurect this thread to ask an important question. What is the name or part number of these little mp3 players? The link is dead again and the search engine on the website of the supplier is broken. If anyone has a good link the name/part number, please post it for us late comers.

Thanks!!!


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## Otaku (Dec 3, 2004)

The MPJA part number is A-MP016. I've seen it one or two other places under the same part number, too.

Found it here: http://www.watchcloseouts.net/ecommerce/Scripts/prodView~idproduct~618.htm

I called MPJA - they're having web site problems, but do have the item in stock. 1-800-652-6733


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## Devils Chariot (May 23, 2007)

*super plus thanks bro!!*



Otaku said:


> The MPJA part number is A-MP016. I've seen it one or two other places under the same part number, too.
> 
> Found it here: http://www.watchcloseouts.net/ecommerce/Scripts/prodView~idproduct~618.htm
> 
> I called MPJA - they're having web site problems, but do have the item in stock. 1-800-652-6733


Come tuesday I'm on it!...and I thought you would all be too busy watching Army of Darkness on AMC to reply. Thanks!!!


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## TwistedDementia (May 2, 2007)

I got my 5 in and thier perfect for prop's just like you said, thank,s again for the post Otaku!


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## Dr Morbius (Sep 21, 2004)

AND the circuit works for other things too! Good things. Oh yes.


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