Search found 87 matches

by Viking
Tue Aug 05, 2008 11:27 pm
Forum: General Discussion
Topic: help on DC-AC inverter for Public art Project. Thks
Replies: 168
Views: 40709

Hello Federico, We will still use 3700 pixels, and the receivers will operate as if it had the full 200. But some of the panels, and four in particular, will not be populated with the full set of shift registers and pixels. If we make the shift registers modular then we can populate each panel with ...
by Viking
Tue Aug 05, 2008 10:38 am
Forum: General Discussion
Topic: help on DC-AC inverter for Public art Project. Thks
Replies: 168
Views: 40709

Hello Federico, With the 1k resistor, the gate current of the triac is only just enough to trigger it on. We would go for something around half that value if operating of a 5V supply to ensure all triacs were turned on. For de-coupling it is a combination of supply filtering and careful circuit layo...
by Viking
Tue Aug 05, 2008 10:01 am
Forum: General Discussion
Topic: help on DC-AC inverter for Public art Project. Thks
Replies: 168
Views: 40709

Hello Federico, That’s good news about the triac, I was never quite sure if this was going to work. Were you driving the triac gate from a 5V logic signal through a suitable resistor to give you a minimum gate current of 3mA, something like a 680R resistor should give you about 5mA, 1K would give ...
by Viking
Tue Aug 05, 2008 6:38 am
Forum: General Discussion
Topic: help on DC-AC inverter for Public art Project. Thks
Replies: 168
Views: 40709

Hello Dyarker, yes I agree, this may not work, hence the need to test this as soon as possible.
dyarker wrote:I don't think I agree about TRIACs at such low current, but I'll let that alone for now (too many cooks ...) Procede with the testing.
Regards
Rob
by Viking
Tue Aug 05, 2008 3:37 am
Forum: General Discussion
Topic: help on DC-AC inverter for Public art Project. Thks
Replies: 168
Views: 40709

Hello Federico, Yes, your summary is correct. There will be a single RS485 line daisy-chaining the 28 panels and that it apart from the power. With a 5 bit channel selector we have 0-31 channels that can be selected, of which we need only 28. No individual select lines needed. [One question, what do...
by Viking
Mon Aug 04, 2008 11:52 am
Forum: General Discussion
Topic: help on DC-AC inverter for Public art Project. Thks
Replies: 168
Views: 40709

Hello Federico, Here is a quick sketch of the modified DMX with PIC receiver. The PIC can be set to one of 32 panels, we only need 28. The PIC is pre-set to expect to receive 25 bytes of data starting from the pre-set panel number and to ignore all other data. The PIC doesn’t store the data, it si...
by Viking
Mon Aug 04, 2008 4:24 am
Forum: General Discussion
Topic: help on DC-AC inverter for Public art Project. Thks
Replies: 168
Views: 40709

Hello Frederico, I have probably overestimated the number of instructions that are needed within the 4uS time frame. And we can slow everything down about 10 times if we had to. It would be possible to make a ’discreet logic’ receiver, as the process of reading the data from the packet is not th...
by Viking
Sun Aug 03, 2008 3:11 am
Forum: General Discussion
Topic: help on DC-AC inverter for Public art Project. Thks
Replies: 168
Views: 40709

Hello Federico Here is a quick sketch of the DMX timing. http://www.postimage.org/aV1rqyd9.jpg The receiver (micro-controller) would need to be able to cope with events on a 4uS time scale, so would suggest that it should have an instruction cycle sufficiently short to allow 20-30 instructions withi...
by Viking
Sun Aug 03, 2008 12:28 am
Forum: General Discussion
Topic: help on DC-AC inverter for Public art Project. Thks
Replies: 168
Views: 40709

Hello Federico, Yes, as far as I can see, you diagram is correct. The purpose of the two 74132’s is to generate a latch pulse on the rising edge of the CS line and prevent further clocks from reaching the shift register. With the 6818 strobe input low, the outputs remain in their previous state i....
by Viking
Sat Aug 02, 2008 8:50 am
Forum: General Discussion
Topic: help on DC-AC inverter for Public art Project. Thks
Replies: 168
Views: 40709

Hello Federico, I’ve had a more detailed look at DMX and I think we can use this in more or less it’s original, unaltered form. It sends a repeating packet of information with up to 512 individual receiving stations, we would only need 28. Each panel would be assigned a channel number and the da...
by Viking
Fri Aug 01, 2008 10:00 am
Forum: General Discussion
Topic: help on DC-AC inverter for Public art Project. Thks
Replies: 168
Views: 40709

Hello Federico, I don’t see anything fundamentally wrong with this scheme. I see you have a micro controller at the receiving end which actually makes things a lot easier. You could make this work with a single pair of high speed serial lines, data and clock, the select signal would not be needed....
by Viking
Thu Jul 31, 2008 11:10 am
Forum: General Discussion
Topic: GE low voltage lighting
Replies: 18
Views: 4708

These are magnetically latching 2 position switches, so replacing them with solid state versions is not going to be a simple matter. You could replace the momentry control switches with latching switches and use opto-isolated solid state switches, but I'm not familiar enough with this system to know...
by Viking
Sun Jul 27, 2008 11:04 pm
Forum: General Discussion
Topic: help on DC-AC inverter for Public art Project. Thks
Replies: 168
Views: 40709

Hello Federico, Had a quick look at DMX, looks like it is a RS-485 port as far as the hardware is concerned, and transmits data as a packet, repeating over and over again. Looks like it can support 512 individual receiving stations (presumably with repeaters). Could probably be made to work in your ...
by Viking
Sun Jul 27, 2008 8:23 am
Forum: General Discussion
Topic: help on DC-AC inverter for Public art Project. Thks
Replies: 168
Views: 40709

Hello Federico, I was about to suggest using RS-485, as the RS-422 standard only supports 10 receivers on a single line and we need 28. RS-485 will support 32 at least, (and probably more in this particular case). I haven’t heard of DMX, but was refreshing myself on interfaces over the weekend whi...
by Viking
Fri Jul 25, 2008 10:52 pm
Forum: General Discussion
Topic: help on DC-AC inverter for Public art Project. Thks
Replies: 168
Views: 40709

Hello Federico, There is a slight difference between the operation of the interface of the two devices, but will not matter in practical terms since you will need to construct quite an elaborate interface/drive unit between the control (PC?) and the display. Apart from a simple clocked serial interf...