Shum

Hi Goblinz, The inverter I used is made up components found in my sparepart box. The schematic is attached as requested. The 555 Timing chip is wired as a standard square wave generator. The pulses are amplified by the transistor and fed to step up transformer. I used a small 1VA 230V to 9V low profile transformer. A better option would be to use a standard small audio output transformer (available at Radio Shack) with a primary measured 1k Ohm and a secondary of 8 Ohm. With the configuration as shown in the schematic the output of the transformer at A and B varies between 80V to 120V AC (loaded) with a supply voltage of +9 to 12 Volts. To test the circuit, connect a 2 nf capacitor as a load across A and B and switch on the supply. Measure the voltage across these points. It should be around 80 to 120V. The brightness of the Electroluminescent (EL) element depends on the voltage that is applied to it. Shum Edit: I forgot to mention that there is no interference heard over the audio system (with external amplifier). inverter.JPG

Hi Stryd, I used all the materials that I could gather from my little workshop to construct the enclosure. Enclosed hereto are some pictures of my midiboxsid. Thanks Regards Shum

HI, When the package arrived, I emailed Smash to inform him that the package was delivered in good condition. I used the same 15 watt soldering iron to solder all other components without problem. I did not know I could damage the encoders when soldering them in. Anyway I wired up a jig as shown in the attached diagram to test the encoder. The rotation of the shaft either to the rignt or left will cause the LED to flicker. I found 3 encoders with shafts that were slight lose. Under the test, when one touches the shaft the LED flickers thereby giving rise to intermitten problem. The problem could be that of the wipers inside the encoder. I will try to open them up and do the repair. This is a small matter and no claim willl be made. Regards Shum encoder.JPG

I ordered a batch of 20 encoders from SmachTV, and installed them according to the schematic as shown in the SID V2 CS DIN map. Loaded the core with midibox_sid_v2_0_rc25 - 8580 SID application. Most of the encoders work, but some did not work. I spent lot of time troubleshooting the core, the sid module and the Din board. They are fine. I then swap SR and pin around with working encoders and found that the problem was in the encoder itself. Is there a way to test the endcoders prior to their installation. If so it would save much time in troubleshooting. Thanks Shum

Hi Johnc, I am glad to note that you found a solution to your problem. I agree that software implementation is more flexible than hardward option. Good luck with your project! Shum

Hi Stryd, I do not have an enclosure yet, and am in the process of constructing one using plexiglass and wood. I would probably take some time to complete it. BTW how does one post pictures to the forum. The only way I know is to attach them using the "Additional Options". Thanks Regards Shum

Hi nILS and stryd, Thanks for updating the files and I am sure it will be a great help to those who are new to the midibox SID projects. In fact I did try searching the forum many times for the information but was unable to find the answers. Anyway as I mentioned before I did look at the *.setup.asm file and found the correct location where modifications can be made such that J5 could be use as LED display. Now that I have finished the Core, the SID and the DIN modules and wired them up with a midi keyboard and powered up, it all works. I was able to play notes from the keyboard. At the moment I am using the 6581 SID and it operats on a 5V and 12V supplies. I found that the SID chip is warm to the touch, is this normal. However, the 5V and the 12V regulator chips remain cool (room temperature). I am using a 2x40 LCD with EL backlight and have built a small inverter to power the EL element. Thanks Regards Shum

Hi nILS, Thanks for the information. I went through all the files that I downloaded and could not locate the cs_menu_io_tables.inc. However, I found that the shift LED, CC LED and the Edit LED are located under CS_MENU_DOUT_TABLE. I thought to myself that this must be the place where SR# and PIN# can be modified such that J5 would output these LED functions. I did the modification and put SR# to 0 and pins to A1(pin1), A2(pin2) and A3(pin3) respectively, and recompiled. I tested these buttons and found only the shift LED works when that button is pressed. The other LED did not light up when the respective button is pressed. Thanks again. Regards Shum

Hi, My MidiboxSID kit that I ordered from SmashTV has arrived. It consists of a Core kit, SID kit, and Din kit. I intend to build a simple version first using minimum components before venturing out for a more complex one. As I do not have a Dout kit, I would like to use J5 of the Core to display the Link, CC and Edit functions by LED. I will be using the SID 6582 chips. The information given in the MB6582.asm indicated that “#define Default_J5_Function 0 needs to change to 2" in order to use the pins as digital output. The SR ID has also needs to change from 1 to 0 in cs_menu_io_tables.inc. I searched through the downloaded firmware but was unable to locate this file. Grateful if someone could point me to the right direction. Many thanks. Regards Shum

Hi Johnc, You mentioned that you are comfortable with connecting the ULN in parallel as long as it is on the same chip. As I see it, there should not be any circulating current between different chips driven by different Douts/Cores. This is provided that the 12V and the 0V rails are solidly wired up. Pin 10 of the ULN is a common line where all the flywheel diodes are connected to, and this pin on every ULN must be connected to the 12V rail solidly via a short connection as possible. When switching on or off a magnetic circuit (magnet/relay) voltage transients are produced. The transients if not suppressed will cause failure of the ULN. Especially when switching off the magnet, the electro magnetic energy that is stored in the coil will be released as ‘Back EMF’. This EMF will cause a current to flow through the coil and the diode and dissipates as heat. The more magnets that are connected in parallel the higher is the current that flows through a single ULN (one ULN controls two or more magnets). If the connections were not done appropriately it will lead to eventual failure of the ULN. BTW have you actually paralleled two or more magnets/relays to one ULN of the same chip with success and failed when making parallel connections across adjacent chip?. Instead of connecting the ULN in parallel, would it not be a better way to do it on the DOUT side, please see the attached schematic. The 4066 is a switch, which when switched on will link for example in this case, the C notes of different footage. At the bottom of the schematic is a typical keying configuration of an analogue electric organ. As my knowledge on the pipe organ is limited, I was trying to figure how the pipes are connected similarly but I could not find the answers. After some more thinking an idea came to mind. The second schematic (TOL - thinking out loud) shows how a 16' and 8' pipes can be selected individually or together. Regards Shum ULN.JPG TOL.JPG

Hi Johnc, If you have not had a look at the date sheet for the ULN2803 you can find it at this site. www.st.com/stonline/books/pdf/docs/1536.pdf. It mentioned that the output of each driver can be connected in parallel. I have included the attached diagram to show an equivalent circuit. Please see Fig.1. When both inputs are switched off, the voltage at point “a” will be at +12V. When input 1 is switched on current will flow from the +12V rail through the relay, point “a” and T1 (conducting) to the 0V rail. The voltage at point “a” will fall almost to 0V (the small voltage equals to the voltage drop across T1). No current will flow through T2 as it is not switched on or conducting. If it is now switched on, both T1 and T2 will share the current through the relay (half goes through T1 half goes through T2). Figure 2 shows an equivalent circuit. Based on the data sheet for the ULN, it is my opinion that there should not be a problem connecting the output of the drives across individual chip, provided the +12V rail and the 0V rail on each ULN board are connected solidly. This was already mentioned by XPA. Based on the circuit, theoretically there should not be a problem. Not sure of the problem you are facing. Shum 2803_1.JPG

Hi Grayde, As Jimhenry said the midibox could be overkill to midifying just 13 pedals. There is a simplier circuit which appears at this site http://tomscarff.tripod.com/projects.htm. It uses only pic16F877. The firmware for the pic is provided. Take a look. Good luck Shum

Hi NV, Seppoman is right, enough has been said already and you should get on with the project. In my opinion using a transformer with a higher rating then needed is fine unless the cost differential is not substantial. For your applications, those transformers which have been selected are fine. I have attached a working schematic showing the two PSUs for the Core and the Fm modules. The lower amp output of the transformer is not an issue provided the loading is within this output range. Each 18V winding with a rating of 820mA, provides a stable regulated DC output of +12V and -12V. The maximum current which can be drawn from the +/-12V is 820mA ( 820mA x 2 x 18 = 30 VA) each. If you draw more current than this you will overload the transformer and it will get hot. Regards Shum psu2.JPG

Hi NV, In my opinion, I would go for a Bridge configuration Bipolar power supply (with 2 secondry windings) as it has a lower ripple value of 48% (good for audio application) compared to a half wave configuration (with 1 secondary winding) that has a ripple value of 120%. Figure 1 in the attached schematic is a typical Bipolar power supply. Also I would suggest you use the transformer model # 14A-30-36 with a rating of 20VA from the data sheet you provided. Regards Shum 1bpsu.JPG

Hi NV, You probably be able to get the 12v ct 3A transformer from RadioShack.com. The model # 273-1511 or catalog# 237-1511. The primary is rated at 110v that is what you are looking for. I have used transformer of the same rating for my midibox64 and other projects that require regulated voltages of +/-12 and 5v. Hope this information will help. Regards Shum