Replace relays with solid state circuit

[ericgibbs]

Wow that's a lot simpler. Thanks.

Some questions...

Some of the transistors are not identified, namely Q1, Q2, Q4, Q6. Please identify as type.

Is it OK to use ¼W resistors? I've been using ½W.

Since the ZTX649 is in short supply at my local source, I'll probably use ZTX450 instead for NPN ZTX type, OK? And ZTX751 for PNP ZTX type. And TIP32C where you have specified TIP32, OK?

hi,
Those transistors Q1, Q2, Q4, Q6 can be any general purpose transistor, something like a 2N2222.
If you have any spare ZTX450 use them.

The ZTX types you have named are OK, also the TIP

You can use 0.25W resistors, except for the 330R's.

 

[hiker]

There's something I'm not sure I'm following...

For the anodes, there are 8 USB lines for colour select, however there are 16 colour select circuits (Type B). Are the Type B circuit inputs (labeled "Select Colour") tied together in pairs (i.e. wired in parallel)?

 

[ericgibbs]

There's something I'm not sure I'm following...

For the anodes, there are 8 USB lines for colour select, however there are 16 colour select circuits (Type B). Are the Type B circuit inputs (labeled "Select Colour") tied together in pairs (i.e. wired in parallel)?

hi,
The 8 colour selects from the USB lines control a 'pair' of colour transistor circuits, one for rooom A and the other for room B.

So you will have one USB wire driving two colour Type B cct's. OK.

I was thinking how you plan to control the brightness of the LED's, have you worked out a scheme for that.?

 

[hiker]

From testing brightness, I've settled on a 470R for each cathode and 330R for red anode, none for green. Seems that if I don't use the 330R for red, it is too bright.

Thanks, going shopping now...

 

[ericgibbs]

From testing brightness, I've settled on a 470R for each cathode and 330R for red anode, none for green. Seems that if I don't use the 330R for red, it is too bright.

The idea I was considering was to use LM317's in place of the TIP32's.

You could adjust the best voltage for the Green and Red LED's separately.

Would mean a small mod to the Type 'C' Cct.... whatcha think.?

EDIT:
and 330R for red anode why do you need an anode resistor.? the brightness will change for different numbers displayed.!!!


EDITED:
Forget the LM317 in place of the TIP31...
Having a bad hair day.

 

[hiker]

When experimenting with the bi-color displays, this is what I've found.

All the following tests have cathodes with separate 470R in series for each of 8.

1) 5v to green anode only - green color displayed
2) 5v to red anode (330R in series) only - red color of approximately same light intensity as case 1 displayed
3) 5v to green anode (no resistor) and red anode (330R in series) simultaneously - yellow/orange color of approximately same light intensity as case 1 displayed

4) 5v to red anode (no resistor) only - red color very bright (too much so) displayed
5) 5v to green anode (no resistor) and red anode (no resistor) simultaneously - red color very bright (too much so) displayed (note that red color dominates green in this case)

Note: The brightness does not appear to change for different numbers displayed with any of these scenarios.

 

[ericgibbs]

When experimenting with the bi-color displays, this is what I've found.

All the following tests have cathodes with separate 470R in series for each of 8.

1) 5v to green anode only - green color displayed
2) 5v to red anode (330R in series) only - red color of approximately same light intensity as case 1 displayed
3) 5v to green anode (no resistor) and red anode (330R in series) simultaneously - yellow/orange color of approximately same light intensity as case 1 displayed

4) 5v to red anode (no resistor) only - red color very bright (too much so) displayed
5) 5v to green anode (no resistor) and red anode (no resistor) simultaneously - red color very bright (too much so) displayed (note that red color dominates green in this case)

Note: The brightness does not appear to change for different numbers displayed with any of these scenarios.

hi,
It sounds OK to me.

I would build small sections of the system and do any debuging required.

Lets know how it goes.

 

[hiker]

A couple of observations..

The last setup (Hiker7) does not allow me to switch both green and red anode on at the same time. So if I ever had a need to display the 3rd color (yellow/orange) I couldn't. Correct?

Also note in my test case above:
5) 5v to green anode (no resistor) and red anode (no resistor) simultaneously - red color very bright (too much so) displayed (note that red color dominates green in this case)
By using this property where red color dominates green, I think circuit B might be simplified since the green anode would not need to be switched, i.e., could have a constant +5v. The red anode only would be switched and have no resistor in series. To dim the intensity I could increase the cathode resistors to 680R or more.

What do you think?

 

[ericgibbs]

A couple of observations..

The last setup (Hiker7) does not allow me to switch both green and red anode on at the same time. So if I ever had a need to display the 3rd color (yellow/orange) I couldn't. Correct?
Thats correct.
To control the two anodes would require more circuitry and control lines, also dont forget the increased demand on the main psu.
I understood the yellow colour was not a design requirement.

Also note in my test case above:
5) 5v to green anode (no resistor) and red anode (no resistor) simultaneously - red color very bright (too much so) displayed (note that red color dominates green in this case)

By using this property where red color dominates green, I think circuit B might be simplified since the green anode would not need to be switched, i.e., could have a constant +5v. The red anode only would be switched and have no resistor in series. To dim the intensity I could increase the cathode resistors to 680R or more.
Its possible to do that if it satisfies the application.

What do you think?

hi,
I would consider using LM317's to set the 'best' voltages for the RED and GREEN anode drivers.

 

[hiker]

Hi Eric,

I'm planning to use a 2.25a PSU with 7 adjustable voltages. The link is here.

I do want the ability to switch red and green anodes independently. Here's my thought and I'd like your opinion please.

Use 16 of your Hiker#4a circuits which would be used as Type "B" cct in your Hiker#7 diagram. Eight Hiker#4a cct's would be used for the 8 displays in each room. Then Type "C" would switch between banks of the 8 Type "B" cct's for each room. This would allow me to use some of the parts I already have, ULN2803A and ZTX751. And less total components I think.

I think I could get by with just 2 ULN2803A for the Type B by using pins 11-18 split two ways to control both A and B banks. What do you think?

Also question about Hiker#4a cct...
Are the 47K resistors (the ones from the ZTX751 collector to 0v) really necessary and if so, what function do they provide? The reason I ask is that the cct seems to work just fine without them.

Thanks

 

[ericgibbs]

I think I could get by with just 2 ULN2803A for the Type B by using pins 11-18 split two ways to control both A and B banks. What do you think?

Also question about Hiker#4a cct...
Are the 47K resistors (the ones from the ZTX751 collector to 0v) really necessary and if so, what function do they provide? The reason I ask is that the cct seems to work just fine without them.
They are just loads to ensure the circuit works when testing with no LED's connected, leave them out.

Thanks

This circuit will drive the anodes, [16 total] each controlled by its own input line.

 

[Mike - K8LH]

Please forgive me. I don't mean to distract you folks from the solution you're working on but I can't quite figure out what the OP is trying to accomplish and I was hoping someone could provide a simple synopsis, please?

Is it basically a PC-USB to 16 bi-colored 7-segment displays controller?

Mike

 

[hiker]

Please forgive me. I don't mean to distract you folks from the solution you're working on but I can't quite figure out what the OP is trying to accomplish and I was hoping someone could provide a simple synopsis, please?

Is it basically a PC-USB to 16 bi-colored 7-segment displays controller?

Mike

Yes, that sums it up. The added complexity is that there are 2 rooms with 8 displays in each and I want them switched so that only one set in on at a given time. I had it all worked out with relays but I want to go 100% solid state.

 

[hiker]

This circuit will drive the anodes, [16 total] each controlled by its own input line.

OK, thanks.

I'm curious, is there a disadvantage is using your circuit with ULN2803A? It is simpler consisting of one leg of UNL2803A, two resistors, one transistor.

 

[ericgibbs]

OK, thanks.

I'm curious, is there a disadvantage is using your circuit with ULN2803A? It is simpler consisting of one leg of UNL2803A, two resistors, one transistor.

No disadvantage, just trying to keep the cost down.

 

[hiker]

No disadvantage, just trying to keep the cost down.

Me too. Since I already have most of the components for the ULN circuits, I'll go that route. Thanks.

 

[hiker]

Hi Eric,
I am curious as to why there is a 1K0 resistor at Base of Q9 in this:
https://www.electro-tech-online.com/attachments/hiker7-pdf.22851/

and the first schematic here
https://www.electro-tech-online.com/attachments/esp01-oct-08-gif.22829/
showed a 2K2 resistor.

Please help.

 

[ericgibbs]

Hi Eric,
I am curious as to why there is a 1K0 resistor at Base of Q9 in this:
https://www.electro-tech-online.com/attachments/hiker7-pdf.22851/

and the first schematic here
https://www.electro-tech-online.com/attachments/esp01-oct-08-gif.22829/
showed a 2K2 resistor.

Please help.

hi,
I recalculated the 2K2 to 1K to ensure the single stage transistor Q9 would have more base drive
to ensure saturation for the TIP.
Q6 and Q7 is a two stage and the base drive for Q7 is coming from a higher voltage.

 

[hiker]

OK thanks,

After experimenting some more with the LED displays, I'm probably not going to switch the red and green anodes separately as unfortunately the yellow-orange colour is not consistent with all digits. I'm favoring switching just the red anodes and having the green anodes with constant 5v. As I mentioned before, this works OK since the red dominates the green. Thanks to you I have lots of options.

This would allow me, as you illustrated in Hiker7 diagram that since I only need 8 lines from USB to switch red anodes, to use a 5v line to control circuit TypeC-Select Room. You had figured using 12v to control TypeC-Select Room, so does that make any difference with any of the resistor values as in the circuit diagram Hiker7 TypeC circuit?

 

[ericgibbs]

OK thanks,

After experimenting some more with the LED displays, I'm probably not going to switch the red and green anodes separately as unfortunately the yellow-orange colour is not consistent with all digits. I'm favoring switching just the red anodes and having the green anodes with constant 5v. As I mentioned before, this works OK since the red dominates the green. Thanks to you I have lots of options.

This would allow me, as you illustrated in Hiker7 diagram that since I only need 8 lines from USB to switch red anodes, to use a 5v line to control circuit TypeC-Select Room. You had figured using 12v to control TypeC-Select Room, so does that make any difference with any of the resistor values as in the circuit diagram Hiker7 TypeC circuit?

hi,
Those TypeC values are OK