analogue_mo

Hello @Zam thank you for your reply, I think all the circuits described here go a few steps beyond the simple resistor/zener circuirt in what it comes to achieving over voltage protection. Having a biased zener will only output constant voltage when the current is also constant, and this is not the hypothetical scenario were protecting our IC's from. Most linear regulator IC's out there apply this type of circuit for voltage rectification, so having a linear Voltage Regulator IC implies having an improved "resistor/zener" circuit. After researching a bit about crowbars and Switching Voltage Supplies I found this book by Martin Brown, "Practical Switching Power Supply Design" where is stated: Also found this post about applying a crowbar circuit to the MB6502 power supply I think this is a good overvoltage protection circuit to use as an example, and I will try to apply its topology using a 5V Switching Voltage Regulator. Still need to get a better understanding of SCR specs though.

Hello everyone, thank you for your replies. @latigid on Regarding your initial question, the answer is Yes, this is a simmilar topology to the linear voltage regulator circuit, but it presents slight differences in its operation. Without getting into many details, the presented circuit acts by cutting off the voltage/current instead of making an effort to regulate it. You're also correct about considering the transistors used as the current passing devices. In the maxim article is noted that for the current pass transistors, the following characteristics are crucial for a successful operation of the circuit: VceSAT as this will give us the voltage drop when the transistor is saturated; The transistor speed will dictate the response speed of the circuit; I'm now looking at crowbar circuit examples, and realizing the over voltage detection operation is simmilar with the one in the circuit I presented. Some differences in how the over voltage situation is handled though. My original idea was to apply a couple of this circuits for each SID, not to the power supply itself. Following this scheme I think I could overcome any 'voltage dropping' issue: But I think I need to do some more research on the crowbar circuit as this might definetly be a more complete fail-safe solution. Hello @TK. thank you for your input on this topic. It is great that new C64 Power supplys are available, I currently only posess 1 left out of the 3 original C64s I owned, the remaining 2 died along the way =( This is actually one of the reasons for my concerns. I would still prefer to power my SIDs using the original C64 Power Supply I have left (I think the transformer itself is a beautifull piece and I like to keep it original) but because I've already seen 2 of them failing while operating the actual C64 circuitry, I wouldn't do this without any extra layer of protection, even with the new ones. Also, I think having some flexibility by providing the option for a single voltage power supply is a big big plus, as it might lead the path for a MBSid battery pack(just a fetish). So I guess I'll be digging into crowbars tonight. Thanks for your help once again, I'll be posting whatever I come up with at the end. If anyone out there could help me out with the answer for: what is the Absolute Maximum Ratings for the 8580 chip it would be great. Kind regards, Analog Mo

Hello everyone, Have been in the process of building my midibox SID for years now, but never seem to be able to get around it. Always concerned that once its built, it could be better. So I've been looking and gathering information about the best projects for midibox SID Models, different SID configurations, different front panel options, and most important, different power supplys. Currently trying to figure out the best way to supply my SID circuit, and this seems to be the best 2 options ou there: C64 transformer suplying a 9V linear regulator and a 5 Volt line directly from transformer to the SID Vcc pin Using a 12V-15V power supply to supply both a 9V linear regulator, and a 5V buck converter in parallel. Both of this options leave me a bit weary. Connecting the SID Vcc directly to the transformer would probably prevent me from having a good night sleep ever again, but also I'm not sure how this buck converter works out when bad stuff happens. I imagine that if the unlikely event of the Mosfet on the buck converter would blow up, it could act as a short circuit and expose the Vcc rail to whatever input voltage is receiving(Please correct me if I'm wrong). I've seen lots of Posts in the forum regarding this topic, and was wondering if I could get an engineer's input on the following circuit(no pun intended). A Google search for 'discrete over voltage protection circuit' will reveal this link as one of its first results: https://www.maximintegrated.com/en/design/technical-documents/app-notes/7/760.html The article from Maxim describes how the circuit works in great detail, but here's an overview: This simple protection circuit is composed by: - 3 resistors - 2 PNP transitors - 1 Diode - 1 Zener The circuit provides a power supply line with adjustable over-voltage protection, meaning that once the voltage at the input exceeds a certain level, the circuit will shut down its output power. The maximum current can also be programmed to certain extent by carefully selecting the transistors bias resistors. A simple reversed bias diode is used as a weak moderate protection against power line reverse voltages. I've simulated the circuit and carefully selected the components so that they meet the 8580 Chip Power limits specifications. I actually took this info from the 6581 datasheet, so not really sure if the same values apply, but good enough to use as a case study. 6581 Vdd pin = 9V 25-40 mA 6581 Vcc pin = 5V 70-100 mA I'm using 2 separate circuits in my simulation, one as a protection for the SID Vdd pin, the other for the Vcc pin. Here is the outcome of the following tests: Test 1: Ideal conditions - sim001_stable.jpg I feed the expected voltages(in range) into the circuits, using some moderate loads (around 200 ohm) to pull some current and everything works as expected. The pass transistor Q2 passes the amount of current required by the 200 ohm load, but also imposes a small voltage drop on the line so this should be taken into consideration. Test 2: Over current protection in action - sim002_heavy_load.jpg I started to simulate faulty conditions. First I decreased the resistance of the loads progressively until I reached their smallest possible value (around 1 ohm), so that maximum current is pulled from the pass transistors Q2. After the load resistances goes lower then a certain value, the current through the pass transistor Q2 is kept the same, and does not go higher as it is limited by resistors R2, R3 and transitor Q1 which controls the current flow in Q2. Test 3: Extreme limits near tip off - sim003_heavy_load_over_volt.jpg I started raising both Voltages at the circuit inputs until near their tip off points.The load resistance level was kept the same, so that maximum current flow is expected. In this scenario we can see the maximum current that the circuit will allow to pass, just before its tip off point. For Vcc, when there's a slight over voltage condition, the maximum allowed current will be around 20 mA more then its rated max limit of 100mA. For Vdd, when there's a slight over voltage condition, the maximum allowed current will be arounf 10 mA more then its rated max limit of 40mA. This upper limits are carefully set as to provide some wiggle room for the IC current requirements. Test 4: Over voltage protection in Action - sim004_over_volt_shutdown.jpg I continued to raise the input voltages above their tip off points (6.2V for Vcc and 11V for Vdd). Once the input voltage exceeds the tip off voltage, the circuit cuts off the pass transistors shutting down the power lines to the IC pins. The transistor is kept off until the input voltage level is set lower then its tip off point. Although I seem confident about this circuit's performance, I'm not an engineer, so it would be really great if someone with more expertize could give me their input on how great(or great disaster) would this circuits be as a power protection for the SID power pins. Not so sure this circuit would provide a nice output impedance for the SID chip to work as naturally as possible, without any restraints. What do you guys think? Also, does anyone out there knows the Absolute Maximum Ratings for the 8580 chip? Kind regards, analog_mo

Thanks, This seems to be exactly what I wanted/needed. MPLAB compatible, USB powered and fancy IC holder thingy; I'm gonna give it a try! Regards, Mo

Thank you very much for your help ! You're a lifesaver I would never had figured this out by myself! I'll probably buy a new programmer since my old one is falling to pieces, I would like to ask if anyone out there knows of a good USB programmer??? Regards, Mo

I'm using the PICburner module from ucapps, the pbrennerNG44 software from sprut.de to burn and MPlab to code n compile. I haven't tried to write the config bits in the code itself but i'll try to do this. Thanks for the tip. Mo

Hello to all. After successfully creating a couple of 16f84a projects I finally decided it was time to move on to the next level. I started experimenting with the pic16f88. I started by creating a really simple code that would toggle every port of the pic at a predefined rate. My goal was to try and use as many pins as possible so I disabled MCLR pin to use it as an output and used the Internal clock Osc to get two more I/O pins; I compiled and I burned with no problems! Then I changed my code a little(changed the toggle rate time) and when I pressed "Identify pic in Programmer" in the "PbrennerNG" softwarethe PIC was allways recognized as a "16f84" wich lead me to believe that the pic wasn't getting reconized at all. If you try and press this button with no pic placed in the programmer, it will tell you there's a pic16f84 in it. My first thoughts were: "$#!- I got a messed up pic". So I got a fresh new 16f88 out of the box and repeated the whole procedure. Everything went fine, the PIC got successfully burned and the program worked. Once again, when I tried to reburn this PIC I was unable to do it as the PBrennerNG software started recognizing it as a "PIC16F84". So I realize it wasn't about the PIC, It's probably something about the configuration bits! Does anyone out there knows how to resolve this? I've already tried and checked the "Vpp before Vdd" box but that didn't doany good. Any help is apreciated, thanks in advance. Mo

Hi nILS, Yeap, I started by uploading MIOS_v1_9g....yet, I did it only once.....I never got to re-upload it but Ill try and do it later on. Right now I'm all about testing this new wonderfull toy =) I'm going for the full step C surface so there is still some work to be done. Going back to the lab.....keep midiboxin!Cheers. analogue_mo

Well, I just found out what the problem was...Apparently I've got a messed up PIC. First I took it from the midibox_sid and tested it in a separate core module I had laying around. I uploaded the midio128 app and got the same response from the SRIO chain(the button connected to D7 outputs a bunch of midi messages and none of the other buttons works). Now I know that the problem is not on the core module. Lucky for me I allways tend to order this kinds of things in pairs, so I had another fresh PIC 18F4685. I stuffed it into the midibox sid core module, uploaded the midibox sid app and everything started functioning.

Hello to all! I'm currently building a midibox sid using aviswhowtech's parts. My current setup is: -mbhp_8xsid_c64_psu_optimized; -pic core with pic18f4685 and 4x20 LCD; -2x sid modules (for stereo sid); I've uploaded the sid test_tone app and everything turned out alright, i got a triangle waveshape output on each of the sid modules. When i connected the SRIO chain to the core module for the minimal configuration setup(9x buttons + 1 encoder) and using the standard pin setup, i realised that only the button connected to SR1 D7 would react on the midibox. My first reaction was to test the SRIO chain with an arduino and check if the buttons were responding properly. The test was 100% successfull so i guess the problem wasn't about the shiftRegisters or short circuits on the SRIO chain modules. After some toubleshooting and investigation I realised that I was getting the problem described here in the section "Testing Shift Registers Connections" (almost at the end of the page). I think this is my problem cause I've uploaded midio128 app and once the SR1 D7 button is pressed it will make the midibox output a bunch of midi notes and cc messages. So I've uploaded the srio_interconnection_test app in order to check the SC and RC pins in my core. The result was unsuccessfull! I got the following voltage values: _____KEY C____________________KEY C#______________KEY D____________ GND__-->__SO = 5V________GND__-->__SO = 0V________GND__-->__SO = 0V GND__-->__SI = 5V________GND__-->__SI = 5V________GND__-->__SI = 5V GND__-->__SC = 0V________GND__-->__SC = 0V________GND__-->__SC = 0V GND__-->__RC = 0V________GND__-->__RC = 0V________GND__-->__RC = 0V GND__-->__VD = 5V________GND__-->__VD = 5V________GND__-->__VD = 5V Then I went searching on the forum and found post so I decided to use an osciloscope to check the signal on pins 21 and 22 of the pic(RC and SC). PIC PIN 21 (RC) PIC PIN 22 (SC) As you can see the signal on pin 22(SC) has much more amplitude than the signal on pin 21(RC). Is this normal?? I apreciate if anyone out there can take some time to help me cause I'm really out of ideas of how i should proceed next. Thanks in advance... analogue_mo

Hello, I was having the same problem trying to program a 16f84a..... I was getting about 22 errors in program and one error in config....fortunately, I already knew that the code wasn't the problem, cause I've used it before and successfuly burned the pic... It turned out to be a hardware problem....I had a faulty transistor(bc337) that was not shutting Vpp off, so, no matter what code I would use, I would allways get the same errors! here is a link to the thread that described this symptoms http://www.midibox.org/forum/index.php/topic,14111.0.html after replacing the transistor everything went perfectly! So my advice is: -Make sure that you're passing all hardware tests; -In order to help you debug your burner module follow this thread: http://www.midibox.org/forum/index.php/topic,14114.0.html Good luck!

hello, I don't actually know how to solve your problem, but my advice is: 1-Use a multimeter to check what voltage your getting from your dc power supply; 2-Check how many Amps your DC is outputting (I'm not really sure but I believe it should be 500mA to suply the pic burner); 3-Make sure you are plugging the DC power suply into the right place, I've managed to explode my 7805 by connecting my power source to the probe plugs by accident; Now turn ON the pic Burner.... 3-Check the voltage your getting after the LM317 power suply circuit stage(you should manage to use the trimpot to adjust its output to 12-13V); 4-Do the same for the 7805(it should be outputing 5V); 5-Now check if you are getting voltage into your ICs: on IC3 : -put the black probe of your multimeter on PIN 7 (GROUND) and the red probe on PIN 14 (VSS) and check if your multimeter is reading about 5V; on IC4 : -put the black probe of your multimeter on PIN 7 (GROUND) and the red probe on PIN 14 (VSS) and check if your multimeter is reading about 5V; 6-In order to debug your PC connections: 6.1-open your burner (p18 or PBrenner) software and select 'HARDWARE' TAB after selecting 'OPTIONS' TAB.Now you have those little buttons that turn the circuit leds on and off; on IC3: -put the black probe of your multimeter on PIN 7 (GROUND) and the red probe on PIN 1 (VPP enable); -Now press the 'VPP ON' button on the burner software and check if your multimeter indicates that voltage does'nt exist(it should be around 0V); -Now press the 'VPP OFF' button on the burner software and check if your multimeter indicates that voltage does exist(it should be around 5V); -put the black probe of your multimeter on PIN 7 (GROUND) and the red probe on PIN 13 (VDD enable); -Now press the 'VDD ON' button on the burner software and check if your multimeter indicates that voltage doesn't exist(it should be 0V); -press the 'VDD OFF' button on the burner software and check if your multimeter indicates that voltage does exists(it should be around5V); on IC4: -put the black probe of your multimeter on PIN 7 (GROUND) and the red probe on PIN 1 (CLOCK); -Now press the 'SCLK ON' button on the burner software and check if your multimeter indicates that voltage exists(it should be around 5V); -Now press the 'SCLK OFF' button on the burner software and check if your multimeter indicates that voltage doesn't exists(it should be 0V); -put the black probe of your multimeter on PIN 7 (GROUND) and the red probe on PIN 6 (DATA OUT); -Now press the 'SDATA ON' button on the burner software and check if your multimeter indicates that voltage exists(it should be around 5V); -press the 'SDATA OFF' button on the burner software and check if your multimeter indicates that voltage doesn't exists(it should be 0V); -put the black probe of your multimeter on PIN 7 (GROUND) and the red probe on PIN 13 (DATA IN); -Now press the 'SDATA ON' button on the burner software and check if your multimeter indicates that voltage exists(it should be around 5V); -press the 'SDATA OFF' button on the burner software and check if your multimeter indicates that voltage doesn't exists(it should be 0V); 7 - If all of this tests are passing so far that means that you have a good LPT cable and that your computer is comunicating with your programmer hardware, so now you should check your ICs output voltages in order to ensure that this chips are working properly: on IC3: -put the black probe of your multimeter on PIN 7 (GROUND) and the red probe first on PIN 11 then on PIN 12 (VDD); -Now press the 'VDD ON' button on the burner software and check if your multimeter indicates that voltage is about 5V on both PINS(11 and 12); -Now press the 'VDD OFF' button on the burner software and check if your multimeter indicates that voltage doesnt exist(it should be around 0V); -put the black probe of your multimeter on PIN 7 (GROUND) and the red probe on PIN 10 (VDD led); -Now press the 'VDD ON' button on the burner software and check if your multimeter indicates that voltage doesn't exist(it should be 0V); -press the 'VDD OFF' button on the burner software and check if your multimeter indicates that voltage does exists(it should be around5V); -put the black probe of your multimeter on PIN 7 (GROUND) and the red probe first on PIN 4 then on PIN 5 (VPP); -Now press the 'VPP ON' button on the burner software and check if your multimeter indicates that voltage is about 0V on both PINS(4 and 5); -Now press the 'VPP OFF' button on the burner software and check if your multimeter indicates that voltage is about 5V on both PINS; -put the black probe of your multimeter on PIN 7 (GROUND) and the red probe on PIN 6 (VPP led); -press the 'VPP ON' button on the burner software and check if your multimeter indicates that voltage is about 5V; -press the 'VPP OFF' button on the burner software and check if your multimeter indicates that voltage does'nt exist(it should be around 0V); on IC4: -put the black probe of your multimeter on PIN 7 (GROUND) and the red probe first on PIN 9 then on PIN 10 (DATA IO); -press the 'SDATA ON' button on the burner software and check if your multimeter indicates that voltage exists on both pins(it should be around 5V); -press the 'SDATA OFF' button on the burner software and check if your multimeter indicates that voltage doesn't exists on both pins(it should be 0V); -put the black probe of your multimeter on PIN 7 (GROUND) and the red probe on PIN 4 (CLOCK); -Now press the 'SCLK ON' button on the burner software and check if your multimeter indicates that voltage does'nt exist(it should be around 0V); -Now press the 'SCLK OFF' button on the burner software and check if your multimeter indicates that voltage is about 5V; 8 - Ok, if you've passed all the tests and still don't manage to work with your programmer then it can only means that you've missplaced or forgot some component. So you should re-check that all components are there and that they're correctly connected. Ensure that polarity of transistors and diodes is correct. Also You should be 100% positive that all components are healthy. This turned out to be a bigger reply than I was expecting, I've been recently debugging my programmer.It was giving me problems because of a faulty transistor, without this tests I would never had figured it out, so I hope this can help others with solving theire programmers problems.... Cheers

Solved! It really was a bad baaaad BC337! replaced it, and now I get 0V between MCLR and Ground when the VPP is off.... Hope this can help anyone else out there. Cheers ;)

Hello everybody, I've been working with my PIC BURNER in this last couple of days, and I've been founding some problems, so, while I was browsing the forum for some answers I found this topic and decided to jump in. The exact same thing happens to me also, Vpp led goes ON when I turn the burner ON....and it only goes OFF after pressing Vpp ON and Vpp OFF buttons in PBrenner.. I have no printer installed, but I have a printer emulator(that prints stuff into pdf files)..... I've been getting other problems but I've created a new topic for this. cheers

I think I've burned my PIC BURNER My problem is that when performing the hardware tests on PBrennerNG software I allways get the same Voltage value between PIC MCLR and PIC GROUND pins. I supose that once the Vpp button  is off, there should'nt be any Voltage between this two pins, am I right? I'm not an electronics expert I only know few basic stuff but I've  tried to 'read' the circuit layout and assumed that the BC337 is working as a gate that once it is opened drains all the Voltage to the Ground, closing the Power supply circuit, so that MCLR PIN never gets to have any Voltage available. I've tried to short the BC337 emiter and collector pins and successfully got 0V between PIC MCLR and PIC GROUND pins.... So I've measured all important Voltages in order to try to understand where the problem was and got the following values: --------------------------------------------------------------------------------------------- --> VPP OFF: Voltage between IC3 pin 9 (ground) and IC3 pin 4 and 5 (goes to BC337 base pin) = 5V (4.96V) Voltage between IC3 pin 9 (ground) and IC3 pin 6 (red led) = 0V Voltage between IC3 pin 9 (ground) and BC337 base pin = 5V (actually it goes around 4.38V) Voltage between BC337 collector and emitter pins = 0V voltage between PIC MCLR and PIC GROUND = Vpp (12.47V ) <-- --------------------------------------------------------------------------------------------- --> VPP ON: Voltage between IC3 pin 9 (ground) and IC3 pin 4 and 5 (goes to BC337 base pin) = 0V Voltage between IC3 pin 9 (ground) and IC3 pin 6 (red led) = 5V (4.71V) Voltage between IC3 pin 9 (ground) and BC337 base pin = 0V Voltage between BC337 collector and emitter pins = Vpp (12.47V ) voltage between PIC MCLR and PIC GROUND = Vpp (12.47V ) <-- --------------------------------------------------------------------------------------------- So, my conclusion is that I need to replace the BC337 cause it's flowing current trough emmiter collector even though the base Voltage is 0V, and current doesn't flow when Vb = 4.38V .Shouldn't this be happening the oposit way? Before I start unsoldering I've decided to ask some advice from the experts out there, so that I don't make a bigger mess out of this. I think I've managed to destroy 3 16F84A so far.... Any help is apreciated, thanks in advance.