mutley Posted November 20, 2008 Share Posted November 20, 2008 Although already mentioned on another thread, I thought I'd post it seperately to a new topic with a more relevant title so that more people may find it to make use of it. If you need a signal voltage inverter to use a Strand (0 to NEGATIVE 10 volts) dimmer with a "standard" (0 to POSITIVE 10 volts) desk, or vice versa, I have designed a 12 channel circuit that will normally operate from either the desk or dimmer's auxiliary DC power feed of 12-35v, on pin 7 of the 8 pin DIN connector. Therefore, it is not normally necessary to need an external DC power supply. This circuit generates a negative voltage from the positive one, and then feeds the signal into an op-amp to invert the voltage level. I have designed this PCB myself, and I am happy for people to use it, but NOT to sell or hire it out in any way. IT IS CURRENTLY STILL EXPERIMENTAL AND HAS NOT BEEN FULLY TESTED YET! Hopefully I'll finish assembling the circuit this weekend and post results here.Full parts list (with CPC order codes) below. It will actually invert in the opposite way as well! ie; If using a Strand analogue desk with a negative output, it will convert it to positive for use on "normal" dimmers. (powered either from dimmers or external power supply: 12-35v DC, centre positive - remove power source jumper!) :up: It must always be powered from a POSITIVE power supply, either from the desk or dimmers, or external, but if a negative supply voltage is connected, it is diode protected so it will not cause damage or failure. To make the PCB yourself, you could try inverting the PCB image (flip it back-to-front), print it on a laser printer with heavy/dark toner setting, use a very hot iron to transfer the toner straight onto copper-clad board, then etch in Ferric Chloride. Scale the PCB to exactly 94mm x 58mm to the outer border line. Input side is the side with the DC power socket (the bottom as you look at the PCB layout in these pictures). PCB layout: www.nwhoodz.pwp.blueyonder.co.uk/vinvpcb.gif http://www.nwhoodz.pwp.blueyonder.co.uk/vinvpcb.gif Component layout (if you want to stick this to the component side of the PCB to make it easier): www.nwhoodz.pwp.blueyonder.co.uk/vinvlabl.gifhttp://www.nwhoodz.pwp.blueyonder.co.uk/vinvlabl.gif Component layout with pads (NOTE: 3 jumper wires required - shown): http://www.nwhoodz.blueyonder.co.uk/vinvcomp.gifhttp://www.nwhoodz.pwp.blueyonder.co.uk/vinvcomp.gif Component list (with CPC order codes and prices not inc VAT): 1x Aluminium box, EN81244, £1.841x 2.5mm DC power socket, CN05839, £0.451x 555 Timer IC, SC04598, £0.213x LM324 Quad op-amp, SC07989, £0.22 each1x 15v voltage regulator, SCL7815CV, £0.35 [soldered onto board with its metal tab to the DC socket, and body towards the capacitors)3x 470uF 35v electrolytic capacitor, CA04759, £0.90 for a pack of 106x 0.1uF capacitor, CA05583, £0.35 for a pack of 51x 1nF capacitor, CA05508, £0.30 for a pack of 54x 1N4001 diode (or similar), SC07337, £0.40 for a pack of 104x PCB supports, PC00359, £3.25 for a pack of 201x 5mm LED (power indicator), SC07653, £0.50 for a pack of 51x 1k resistor, RE.25CF1K, £0.19 for a pack of 1025x 10k resistor ±1%, RE03723, £0.45 for a pack of 501x 2k resistor, RE03739, £0.45 for a pack of 5012x 100 ohm resistor, RE03791, £0.45 for a pack of 1001x 3pin jumper strip (optional), CN00870, £0.59 for a strip of 40 pins1x Pin jumper (optional), CN01411, £0.69 for a pack of 104x 8 pin DIN chassis mount sockets, AV05021, £1.72 for a pack of 51x 94mm x 58mm PCB (however you want to make that, or buy one off me, tin plated and pre-drilled for £6.50 inc P+P)The jumper pins are to select the following:Short pins 1-2: power supplied by dimmerShort pins 2-3: power supplied by desk (position shown in layout above)Not connected: Use external power supply, desk/dimmer power not connected.PLEASE NOTE: pin 7 (supply power) is NOT connected through from input to output. (If you are using this inverter, the chances are that the supply voltage from each unit will be the opposite polarity too! Not Good! :o ) Simply solder a wire between pin 7 on all the DIN sockets if you definately want this - check first! :) 8 pin DIN wiring: For pin numbering, please see this page (not associated with me):http://freespace.virgin.net/tom.baldwin/pinout-8din.htmlPULSAR USERS: If you are using Pulsar dimmers or control, you will need to change your wiring according to the pin layout shown by this link. (Either in the wires from the DIN socket to the PCB, or in an adapted control signal lead) Anything else? Please IM me! Link to comment Share on other sites More sharing options...
boatman Posted November 20, 2008 Share Posted November 20, 2008 There are a few things you need to consider on your board. PM sent. Link to comment Share on other sites More sharing options...
mutley Posted November 21, 2008 Author Share Posted November 21, 2008 I'm about to start soldering the rest of the components in place to test it tomorrow. Taking boatman's PM comments into consideration, I'm thinking about designing a "version 2" - a big brother to this one, and making a few changes, including:Automatic configuration for negative/positive input/output, eg; a negative supply voltage from the dimmer and a positive supply voltage from the desk, would automatically configure the unit to invert the desk's positive output to negative for the dimmers! DIP switches would also be provided for manual configuration "just in case".Automatically source it's power from the supply voltages from the dimmer and desk depending on polarity! Eg; in the same scenario as above, the positive supply for the circuit would come from the desk, and the negative from the dimmer, and the onboard inverter would not be used. If only the desk say, was supplying a voltage, the onboard inverter would be used to generate the inverted voltage.A stronger inverter to provide more current and less dropout as load increases. (At the moment the circuit may struggle to give 12x full level inverted outputs from a 12v supply - I'll find out soon!)A low power warning in case the inverted voltage isn't enough to give full scale.I'm also thinking of making a relay switch unit. You can get DMX switches, but I've not seen many analogue switches. I'm thinking of simply adding a few extra components to make the op-amp into a comparator, and using a simple 5.1v zener diode as a common reference level, so it would switch the relay on when the input is set above 51%.A lot of establishments have a DMX desk and analogue dimmers, and buying a DMX switch with all sorts of unnecessary bells and whistles, at over £60 is pointless when all they want to do is trigger a smoke machine! (I have this exact situation at the moment!) A simple comparator circuit would cost about £5 to build (fully assembled and boxed), and be more flexible. A row of PCB mounted termals would give NO, NC, Common, and spare links (for Neutral and Earth) to enable the user to supply power to something from the unit, or just switch two seperate isolated terminals on or off like in the case of triggering a cheap smoke machine or battery powered device (You don't want mains voltage in a low voltage device - it lets the magic smoke out with some degree of ferocity!) Again, please feel free to make suggestions for inclusion in this project... To be honest, I'm not that interested in making DMX-based circuits. Because as useful as they are, they are readilly avaliable, and by the time I've wasted a dozen hours of my life designing the circuit, I could've just spent an extra £15 buying one off the shelf and soldering it together in about 20 minutes! (or bought a pre-assembled one off ebay!) Besides, a lot of DMX kits use a pre-programmed PIC chip to interface the DMX signal, and I'm not spending £30 on a PIC programming board, and another dozen hours of my life to work out how to program the damn thing, just to make a handful of circuits. If, however, somebody can come up with a cheap DMX receiver circuit using a standard RS485 IC such as the Linear Technology LTC485IN8, that might persuade me to consider looking at making things like mini DMX remote switches to control non-DMX devices like cheap smoke machines, low voltage devices, etc. Until then, I'll stick to doing analogue circuits! Link to comment Share on other sites More sharing options...
boatman Posted November 21, 2008 Share Posted November 21, 2008 I'm about to start soldering the rest of the components in place to test it tomorrow. Taking boatman's PM comments into consideration, I'm thinking about designing a "version 2" - a big brother to this one, and making a few changes, including:Automatic configuration for negative/positive input/output, eg; a negative supply voltage from the dimmer and a positive supply voltage from the desk, would automatically configure the unit to invert the desk's positive output to negative for the dimmers! DIP switches would also be provided for manual configuration "just in case".Automatically source it's power from the supply voltages from the dimmer and desk depending on polarity! Eg; in the same scenario as above, the positive supply for the circuit would come from the desk, and the negative from the dimmer, and the onboard inverter would not be used. If only the desk say, was supplying a voltage, the onboard inverter would be used to generate the inverted voltage.A stronger inverter to provide more current and less dropout as load increases. (At the moment the circuit may struggle to give 12x full level inverted outputs from a 12v supply - I'll find out soon!)A low power warning in case the inverted voltage isn't enough to give full scale. They all sound like useful features. It's getting close to being a commercial product. I'm also thinking of making a relay switch unit. You can get DMX switches, but I've not seen many analogue switches. I'm thinking of simply adding a few extra components to make the op-amp into a comparator, and using a simple 5.1v zener diode as a common reference level, so it would switch the relay on when the input is set above 51%.A lot of establishments have a DMX desk and analogue dimmers, and buying a DMX switch with all sorts of unnecessary bells and whistles, at over £60 is pointless when all they want to do is trigger a smoke machine! (I have this exact situation at the moment!) A simple comparator circuit would cost about £5 to build (fully assembled and boxed), and be more flexible. A row of PCB mounted termals would give NO, NC, Common, and spare links (for Neutral and Earth) to enable the user to supply power to something from the unit, or just switch two seperate isolated terminals on or off like in the case of triggering a cheap smoke machine or battery powered device (You don't want mains voltage in a low voltage device - it lets the magic smoke out with some degree of ferocity!).. Now that could be a really useful box for anyone who has a DMX desk with a demux and analogue dimmers. Utilising a spare demux output for relay control is much cheaper than a Milford DMX relay board. Link to comment Share on other sites More sharing options...
mutley Posted November 22, 2008 Author Share Posted November 22, 2008 OK, it's 3am, and I've finally got round to finishing assembling the PCB (after a few glasses of the old wobble juice!) I can't test it in use yet, because I don't have a lighting desk and dimmer set up in my house, but on no-load tests, with a laptop power supply, the inverted voltage is -11.7vI don't know how well this will hold up when there are 12 dimmer channels running at full power connected, but I'll find out soon! Data with no load (no input or dimmers attached):Input voltage: 20.77vRegulated voltage: 15.14vInverted voltage: -11.76 (a loss of 3.5v)Total current draw: 56.4mA (16mA for the power LED)555 oscillation freq: 85.4kHz The 555 does get slightly warm, as does the voltage regulator, but neither are anything to worry about. Conclusion to follow after testing with desk & dimmers, although I'm starting to suspect that the 555 inverter circuit might not be powerful enough... Watch this space! Link to comment Share on other sites More sharing options...
themadhippy Posted November 22, 2008 Share Posted November 22, 2008 More interest here for an analogue (- 10 please) relay,its something I've been meaning to play around with but time is never available. Link to comment Share on other sites More sharing options...
mutley Posted November 22, 2008 Author Share Posted November 22, 2008 More interest here for an analogue (- 10 please) relay,its something I've been meaning to play around with but time is never available. OK, I'm starting to think about doing this...I'm trying to decide whether to go for a single channel unit, using a 6way spitter from the DIN plug down XLR or phono, OR a 6way unit.Obviously, a 6way will cost a lot more, but if only one channel may be needed, it's extra expense...Actually, what I might do, is make the PCBs stackable, so that you can have just one, or however many you want, all in the same box... Please feel free to put your ideas forward, and suggest things. Link to comment Share on other sites More sharing options...
themadhippy Posted November 22, 2008 Share Posted November 22, 2008 What about some sort of backplane carrying power and control Link to comment Share on other sites More sharing options...
mutley Posted November 23, 2008 Author Share Posted November 23, 2008 I'm probably going to go along the route of two different units:A 19" rack mounted 6-way unit running off mains power, with IEC switched mains outlets, as well as isolated NO and NC terminals for non-mains switching. Obviously, being 6-way is going to mean consideration for current draw across 6 channels. I'm thinking of just a standard 13A supply (for economy), but possible to upgrade the unit to 32A...?A single unit, powered by the aux DC supply on the DIN feed regardless of polarity or voltage, (with an alternative DC input for equipment without aux power supply on DIN). This unit would have a 6-way selector (rotary switch?) for which analogue channel it is operated from, and a DIN outlet for daisy-chaining modules on the same "branch". A mains input via an IEC connector, with switched mains IEC output would be provided, as well as isolated terminals for non-mains switching.With a bit of thoughtful design, both units could use the same PCB, with very few alterations necessary to configure the circuit for whichever unit it will be used in. :) Returning to the analogue voltage inverter, I may abandon the idea of it being "mains free". I have one more inverter circuit idea in mind, but if that is not up to the job, the unit will simply be mains powered. Although not relying on a mains supply is slightly more convenient, it is increasing the cost and complexity of the circuit, and a mains supply would just resolve a lot of things and make it a lot easier! Any thoughts or ideas considered... Link to comment Share on other sites More sharing options...
bh00 Posted November 23, 2008 Share Posted November 23, 2008 Have you tried looking into isolated DC-DC conveters, such as these to give you -12v from +12v. Link to comment Share on other sites More sharing options...
mutley Posted November 23, 2008 Author Share Posted November 23, 2008 Have you tried looking into isolated DC-DC conveters, such as these to give you -12v from +12v. I've considered them, but they tend to have a limited output current of about 10mA. I've just made a few adjustments to the values of components on the existing circuit, and now, I'm confident that it will be able to supply enough negative current:1nF capacitor becomes 10nF (capacitor marking: "102" becomes "103")The two 470uF electrolytic capacitors nearest the 555 become 1000uF I've just tried it and even with a 7 LED car sidelight lamp, the negative voltage drops exactly 1v to -11.27v The slower oscillation of the 555 (down to 8.6kHz) means that less current is being lost through the smoothing capacitor to ground. Unfortuantely, I wasn't able to test the circuit today, as I didn't have access to the venue... Although I did pick up the bits to start looking at, and prototyping the analogue controlled relay... Link to comment Share on other sites More sharing options...
mutley Posted November 25, 2008 Author Share Posted November 25, 2008 Just in case you were wondering about the success of this circuit, I'm really struggling to find any time in the preparation of next week's production, to test it in action. So I'm sending the unit to Boatman for him to play with, and await his results... It should be posted tomorrow. Link to comment Share on other sites More sharing options...
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