Thanks, I'll have to soak this in tomorrow, I'm tied up today. I'm assuming it's something to keep the solenoid from turning on when I power on the whole thing...

Correct. I need more than ten words to make this a proper post.

 

I've updated my drawing with the power reset circuit you drew, thanks.
I'm looking at translating this to a pcb now, and running into problems using 3 single digit display right next to each other... You just can't hardly get'm connected properly.
I had planned on using a single unit (one 3 digit display) but then I couldn't figure out how to get the middle decimal place to show up, being multiplexed the I have them. Can this be done? A single 3 digit display would greatly simply life!
Unfortunately, I can't get a 3 digit display in blue. The only 3 digit displays I've found are common anode, so I don't think it'll work for me.

 

I've updated my drawing with the power reset circuit you drew, thanks.
I'm looking at translating this to a pcb now, and running into problems using 3 single digit display right next to each other... You just can't hardly get'm connected properly.
I had planned on using a single unit (one 3 digit display) but then I couldn't figure out how to get the middle decimal place to show up, being multiplexed the I have them. Can this be done? A single 3 digit display would greatly simply life!
Unfortunately, I can't get a 3 digit display in blue. The only 3 digit displays I've found are common anode, so I don't think it'll work for me.

Ah ha! Looking more closing, I see the symbol in my program has the pins for the single digit on the sides of the number, but they're actually on top and bottom, so it will be a lot easier to route to all the pins...

 

With a MC14543 display driver, outputs con be programed for either common anode or common cathode with Ph- pin6, @ VDD for CA as shown, also with second didgit D.Pt . Missing is connection PNPs emitters to +V- VDD

 

If the decimal point ckt did not make sense it is because I screwed up. Using a common anode display, the 14543 segments are active lo, same for DP. The 2N3904 should have been an inverto, not an emitter follower. When 2nd digit is pulled hi, it also turns on NPN pulling collector & DP lo, illuminating only 2nd dig. DP.
If you already have the 14511, the segs can be inverted with 7 NPNs or an array like CA3081 or ULN2003- common emitters.

 

My blue single digits common cath. came in, so I'll try them first. I think I understand what you drew up though for a CA display.

 

I am testing this out in sections on my breadboards. I've got my 3 digit display hooked up and it seems to work. I'm not sure if I've got the right values for resistors or not. Here's some test results:
R13-R18 = 820 ohm (these feed the display from 4511)
R21, R22, R11a = 4.7K (these feed the 3 transistors)

I get a reading of .84 volts across the three 4.7K resistors feeding the transistors, so that would interpret to .28 mA of current into the base (I think)

I get a reading of 8.6 volts across the 820 ohm resistors R13-18, so that would mean I've got about 10.5 mA of current running into each segment.

On Q1 & Q3, I get a reading of 6 volts across the Emitter/Collector.
On Q2 I get a reading is 9 volts (it drops to 6 volts if I disconnect the 820 ohm resistor from the dp)
I thought the emitter-collector voltage would be a lot lower. The Q's are not hot to the touch, just barely warm.

Are these readings good?

 

PS.
The supply for this is a 12 AC/DC adapter

 

I looked at your PDF schematic in post #71.
The transistors are not switches, instead they are emitter-followers with a fairly high voltage loss. Emitter-followers do not need a series base resistor that wastes voltage.

A multimeter cannot read the fluctuationg voltage from collector to emitter.

 

I looked at your PDF schematic in post #71.
The transistors are not switches, instead they are emitter-followers with a fairly high voltage loss. Emitter-followers do not need a series base resistor that wastes voltage.

A multimeter cannot read the fluctuationg voltage from collector to emitter.

So what does this mean? My resistors sizes are okay? Or that I don't need any resistor connecting Q1-3 to the display output of the 4553?

 

You don't need resistors from the output of the 4553 to the bases of the transistors.
The outputs of the 4553 will go low to about +0.5V then the emitters of the transistors will follow at about +1.2V. Since the 4553 multiplexes the transistors then each transistor is turned on for 1/3rd of the total time and the voltage is almost impossible to measure with a multimeter.

 

You don't need resistors from the output of the 4553 to the bases of the transistors.
The outputs of the 4553 will go low to about +0.5V then the emitters of the transistors will follow at about +1.2V. Since the 4553 multiplexes the transistors then each transistor is turned on for 1/3rd of the total time and the voltage is almost impossible to measure with a multimeter.

Okay. (I thought the 4553 display 1-3 outputs went hight to turn on each display)
I don't quite understand it all, but I will just remove the 4.7K resistors then.

 

I thought the 4553 display 1-3 outputs went high to turn on each display.

I just looked at its datasheet and you are wrong. The display outputs go low.
I couldn't find a thread that says if your displays are common-anode or common cathode.

The schematic in post #71 is for common cathode displays. The segment outputs of the CD4511 go high.

 

I just looked at its datasheet and you are wrong. The display outputs go low.
I couldn't find a thread that says if your displays are common-anode or common cathode.

The schematic in post #71 is for common cathode displays. The segment outputs of the CD4511 go high.

Okay, I think I'm following this. SA through SG of the 4511 go high to feed +12 into the segments, (my displays are common cathode.)
But the transistor base goes low to open the display's cathode to ground...

I think I'm ready to set up the next stage in the circuit for testing.
I really need to make a pulse generator to properly test it.

 

I will be powering this with an ordinary 12 V AC/DC adapter. Do you think I need to use a 7812 voltage regulator to give the whole circuit a constant 12v? I was planning on doing that, but if it's not really critical for this circuit I coulod just leave it out.
One reason I'm thinking of leaving it out is because I've heard that these regulators need a couple more volts input than what they're output is, and if down the road, someone happened to use a 12 volt switching power supply, it wouldn't have enough voltage to operate the 7812, causing unnecessary trouble.
If it's not needed, I'd just as soon leave it out.

 

A 12V regulator needs a minimum input of 14V.
But a 12VDC wall wart is not regulated and its voltage might be too high at 18V when it has a light load.

Why not use a 9VDC unregulated 0.5A wall-wart then re-calculate the resistor values for it?

 

Because my water valve solenoid is operated on 12V DC.
I guess I better go ahead and use the 7812, then.

 

As long as it's being powered be a 12 volt 'wall wart' as you call it, it should have enough voltage to properly operate the 7812.

 

You can only guess if a 12VDC wall-wart has a voltage high enough for a 12V regulator.
My computer speakers are powered from a 12VDC/1A wall-wart which measures 16.6VDC today with no load. It might be 14.3V with a 0.5A load but I don't have a 28.6 ohm power resistor to try.

 

You can only guess if a 12VDC wall-wart has a voltage high enough for a 12V regulator.
My computer speakers are powered from a 12VDC/1A wall-wart which measures 16.6VDC today with no load. It might be 14.3V with a 0.5A load but I don't have a 28.6 ohm power resistor to try.

I'll just use the 7812 and make sure my wall wart is big enough to run it The one I've got is a 1 amp, and shows 16.85 volts with no load. The solenoid uses 6.9 watts, so that's not a whole lot.