Status Light Control

[ADWSystems]

I follow your setup. But the current machine side design is mostly solid state, relays and terminal blocks. So changing voltages to signal would be easier than developing another component for the upstream side.

 

[Reloadron]

I still think there is a way to do it with just zeners and PNP (or NPN transistors), but I just can't get the setup.

That could work also. On the sending side you create several voltage levels using zener diodes or whatever. On the receiving end you use a few voltage comparators like the LM339 family and configure window comparators. Hell, I suggested DTMF which uses different frequencies, using different voltage levels would also work.

Ron

 

[ADWSystems]

The easiest thing on the sending side to do is select voltages by relays as the heart of the sending system has only discrete I/O (machine control). The picture I started with was a zener ladder, but that circuit turned on all the lights below the selected one. Not what I'm looking for. So I have been pondering a way to turn off the previous light(s) as the next one is triggered. But I haven't quite put the pieces together yet. I'm sure that someone knows or as a team we'll put the pieces together.

P.S. I probably should have mentioned the @#$% lights are 12V 3W 250mA. @#$% industrial controls are so power hungry, but so rubust.

 

[Reloadron]

The easiest thing on the sending side to do is select voltages by relays as the heart of the sending system has only discrete I/O (machine control). The picture I started with was a zener ladder, but that circuit turned on all the lights below the selected one. Not what I'm looking for. So I have been pondering a way to turn off the previous light(s) as the next one is triggered. But I haven't quite put the pieces together yet. I'm sure that someone knows or as a team we'll put the pieces together.

Using a window comparator will only output for the specific voltage.

Consider the use of a LM3914 in the dot mode. That will give you as many as 10 voltage dependent outputs. One chip package. Then to drive the lamps use single transistor drivers.

Ron

 

[Diver300]

I would just use a serial connection from a UART. You only need to send one character, of 8 bits, so a PIC like a 16F627 would do that fine.

If you want to send a signal on the power wire, you will need a low baud rate, a transistor to drive the line, and a diode and capacitor at the receiving end to keep the power on while the character is being sent.

The UART transmit lines are high when no data is being sent, so that would go through the diode and charge the capacitor. When the character is being sent, there is a "Start" bit, which is low, 8 data bits, and a "Stop" bit which is high. After that the lines goes high again. (As there is no voltage transition at the end of the "Stop" bit if no more data is sent, the end of the "Stop" bit isn't a physical event)

Anyhow, if you just encoded each light as one bit of the 8 that you sent, you can send 8 independent bits with one character. For lights you would only have to send the data maybe 10 times a second at most, so the line would spend most of its time high.

As long as the capacitor could keep the power on the PIC while the line drops low during the transmission, it wouldn't reset. The lights could be powered from the line directly, as they would only turn off for an instant, so there would be no problem seeing which ones are on.

 

[ADWSystems]

I would just use a serial connection from a UART. You only need to send one character, of 8 bits, so a PIC like a 16F627 would do that fine.

If you want to send a signal on the power wire, you will need a low baud rate, a transistor to drive the line, and a diode and capacitor at the receiving end to keep the power on while the character is being sent.

The UART transmit lines are high when no data is being sent, so that would go through the diode and charge the capacitor. When the character is being sent, there is a "Start" bit, which is low, 8 data bits, and a "Stop" bit which is high. After that the lines goes high again. (As there is no voltage transition at the end of the "Stop" bit if no more data is sent, the end of the "Stop" bit isn't a physical event)

Anyhow, if you just encoded each light as one bit of the 8 that you sent, you can send 8 independent bits with one character. For lights you would only have to send the data maybe 10 times a second at most, so the line would spend most of its time high.

As long as the capacitor could keep the power on the PIC while the line drops low during the transmission, it wouldn't reset. The lights could be powered from the line directly, as they would only turn off for an instant, so there would be no problem seeing which ones are on.

Sorry dude. WAY too many pieces. I have already done the cost analysis for a pair of microcontrollers and associated PCB and components. It would be cheaper and easier to run a multi-conductor cable.

 

[Reloadron]

Back to the beginning:

Status Light Control

Here's a design challenge for you all (and me).

I have a series of status lights (four currently, but might be three to six) that I would like to illuminate, one at a time, using two wires, and as few components as possible. There is no order to the lights so a counter would be out.

The driver behind the attempt is to reduce the conductors required in the cables and connector to reduce cost. But too many components in the solution may increase the complexity while not reducing the cost.

My first thought was select the light based on the voltage supplied. I can get two lights if I use a positive and a negative voltage, but that diesn't get me in the 3-6 count required. I also was pondering a zener ladder, increasing the voltage to trigger the next light, but all the previous lower voltage lights would also be on. No go there.

I look forward to seeing what you all come up with.

What is the distance involved? You are running off a controller likely with DO signals you want to use for lamps as status indicators. The controller could be any number of types like PLC, computer driven modules or whatever. You have 12 volt indicator lamps.

The more things you add will obviously add to the drawings as well as add more pieces and parts to worry about or fail. Unless you have a long run between signal out and indicator the best and simple approach is hard wired. The status lamps should share a single common and one wire for each lamp. If the control and status indicators are all in a common cabinet I would just run wires and keep it simple. Just about anything else becomes overkill and added expense.

Just My Take
Ron

 

[mbarazeen]

see the attached circuit, it may work for the purpose, but you should have the right controller at the end to signal the pulse depends on the last status displayed.

in 3 lamps system, say if lamp 3 is on then to make the lamp 1 "on" it may require 8 pulses or less depends on if a reset also wired.

you can select the transistors & regulator depends on the power handled.

Edit: another way to set the lamps without memorizing last status, just make a power off at every time before sending a pulse train to set the lamps, it will reset the counter & make the counts from start.

 

[MikeMl]

All the digital and PW solutions so far violate the "power over the same two wires" requirement.

 

[mbarazeen]

All the digital and PW solutions so far violate the "power over the same two wires" requirement.

i hope my circuit doesn't violate, one end is control end then two wires (one pair) after that display end....

 

[ADWSystems]

Your circuit meets the two wire requirement. After LJCOX post I could picture where you were headed. Instead of the resisitor-transistor pairs, I would opt for a ULN2003. They are wonderful chips for dealing with logic-driving-power circuits.

I wasn't thinking digital when I started the thread. You have all put up some nice options. Unfortunately I would need to device a way to send the pulse count.

I'm hoping to play with SPICE tonight and see if I can figure out how to turn of the preceeding lamps. I think it will be some type of cascade circuit. Such that when Vsig > Z2 it activates a transistor that shuts off the light attached to Z1, then when Vsig > Z3 it activates a transistor that shuts of the light attached to Z2 and Z1.

 

[Diver300]

Sorry dude. WAY too many pieces. I have already done the cost analysis for a pair of microcontrollers and associated PCB and components. It would be cheaper and easier to run a multi-conductor cable.

16F627s are less than £1 in any reasonable quantity. A lot of ICs are that sort of price.

My 2001 car uses multiplexing for the window switches from the driver's door, to save 8 conductors, going through 3 connectors.

What distance are you running?

 

[MikeMl]

The 4017 circuit lets you turn on one lamp at a time. I thought you needed independent control of each lamp, which means that if you have four lamps, there are 2^4=16 different states of lights being on/off.

 

[ADWSystems]

I follow you now Mike. Actually I didn't say. I believe that only one lamp will be lit at a time. I will need to review the requirements and see if I need to light two specific lamps at once. My initial train of thought on the design would only light one specific lamp at a time.

 

[mbarazeen]

Y
Unfortunately I would need to device a way to send the pulse count.

.

its also not so difficult, we can find a way to do it. whats the input you get to make the status? like you would have similar 3 or 6 out puts and only one goes high at a time? or other combination?

 

[ADWSystems]

Only one is on at a time. They will be selected by a relay output. But now I'm adding a circuit to the mix. The price advantage is slipping away.

 

[Reloadron]

Only one is on at a time. They will be selected by a relay output. But now I'm adding a circuit to the mix. The price advantage is slipping away.

What exactly is the price advantage being weighed against?

Ron

 

[ADWSystems]

Component and PCB combine cost versus multi-conductor cable and multi-pin connector combine cost. Two wire and two pins is super cheap. The cost goes up almost exponential as the conductor and pin count rises. Additionally the cost is excellerated by the station count. Cable and connectors assembly cost does not decrease much, if any, with and increase in volume. Where as PCB manufacture, component, and assembly costs have a distinct volume price reduction.

 

[ljcox]

Here is another thought.

Use the LM3914 "in reverse", ie. connect the stair case voltage to RHI and the Sig in to Vref.

The spec indicates that RHI can be connected to V+ & I can't see any reason why you can't connect Sig in to V ref.

 

[Reloadron]

Component and PCB combine cost versus multi-conductor cable and multi-pin connector combine cost. Two wire and two pins is super cheap. The cost goes up almost exponential as the conductor and pin count rises. Additionally the cost is excellerated by the station count. Cable and connectors assembly cost does not decrease much, if any, with and increase in volume. Where as PCB manufacture, component, and assembly costs have a distinct volume price reduction.

Now I much better see what you are working with. Thanks for the explanation. What you have is nothing like what I was seeing.

Ron