At the risk of volunteering to design something that is way over my head, it might use a lot fewer wires to do all the logic in the data entry pad and send serial data to the outside display.

Don't throw things at me!

 

To give you a better idea, if you look behind the motor there is a small board that reads "8.19". Where that board is, is where I would mount the digital board. I sit in front of the motor under the roll cage, and that's where I would need to control the board. Thanks for all the help guys

 

At the risk of volunteering to design something that is way over my head, it might use a lot fewer wires to do all the logic in the data entry pad and send serial data to the outside display.

I agree, unfortunately, the only way I can if of doing this off the bat is using a microcontroller (uC) with a serial-controlled LED IC. While I've got some time to put a digital logic solution together, a microcontroller solution would require more time than I have right now. But giving it a few seconds more thought after reading your post #12, we could probably use a multiplexer/demultiplexer pair! I've haven't used this before, but perhaps a CD4067 pair which appears to reduce 16 wires to four would work. #12, you are brillant! If you are familar or have other thoughts on doing this, I'll look into it. Perhaps a shift register? I've used those with uC's before, but never with digital logic alone. Would that be possible you think?

Don't throw things at me!

I wouldn't dream of it.

 

I'm not gonna lie, a lot of that looks like a different language to me! That being said, that's ok, I am sure I can figure it out. Just will take me some time

 

You may wish to consider using BCD thumbwheel switches; they are reasonably compact, very lightweight, easy to set, and display the numbers directly on the switches themselves.

Jameco is one supplier that carries them.
Here is a thumbwheel rotary BCD switch:
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_26818_-1
Here is a pushbutton-type BCD switch:
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_26789_-1
Each digit has an up-button and a down-button.
You would need three of these BCD switches.
You also need end plates.
You can see all of the switches and available end plates in this list:
http://www.jameco.com/webapp/wcs/st...type=jamecoall&freeText=electromechanical+BCD
You could then use something like a CD4543B BCD to 7-segment display driver, one per digit, to drive the displays:
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_13696_-1

 

SgtWookie,

This is simple and elegant, thank you for your input. Any major difference between the CD4543 and CD4511? I've used the latter before, but couldn't see an immediate difference between the two in glancing at the datasheets. Thanks again.

 

Okay, thanks in no small part to SgtWookie's suggestion, I've put together a pratical (I hope) solution.

I invite constructive critism in case I've missed something.

Big Ragu,

The attached schematic assumes you're making your own seven-segment display by using four 5mm LEDs in series per segment choosing red, orange, or green LEDs. If using blue, you'll have to use three per segment. Alternately, you can use a pre-built 7-segment display - just be sure you choose a common anode (C.A.) display or we'll have to replace the ULN2004 with something else. One place for inexpensive displays is here: http://www.futurlec.com/LEDDisp.shtml.

You can use a DB15 cable and connectors between the two boxes and two large conductor wires such as AWG 18 for the power or a single DB25 cable - just use multiple wires on the DB25 for the power leads.

There's plenty more to comment on, but I'm beat, so I'm calling it a day. Take a look, see what you think, and let me know what questions you have.

 

Ok, for starters, I can't thank you enough for helping me. It is very appreciated. I studied the schematic a bit last night, and a little this morning. I have many questions, but I'm going to start simple. It looks like I need 35 resistors, 4 capacitors, 3 cd4543's, 3 uln2004's, 3 switches, and a bunch of diodes. Here's my first round of questions:
1. The first diode is wired just to show that there's voltage?
2. SW1,2,and 3 I assume are switches like the ones SGT Wookie suggests? What about number 4? Is that just an NO switch?
3. How will I know what resistors to use, as far as ohm and wattage?
4. Are there blank circuit boards available for me to assemble these components to?

This should get me started, I have other questions but I'd like to do some more research before I get to them.

Edit:This is the first time I've ventured into this type of electronic project, and I'm sure that's obvious. I am anxious to learn as much as I can, and I appreciate your patience with me as I go along.

 

The first diode (d1) looks like it for polarity protection, keeps you from letting all the magic smoke out if you connect it backwards.

Here's a source for the perf board, they have a variety to pick from this one has pads to solder to.
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_263207_-1
And just in case you didn't know, all those diodes in series/parallel (d2-d90) are your leds.

 

I studied the schematic a bit last night, and a little this morning. I have many questions, but I'm going to start simple

No problem, I understand this a lot to digest. We normally have people do some research and propose solutions and help them along. As you're not doing this for a school assignment, need something quick, and intend to kinda go head-first into electronics with a project (one of my favorite approaches ), I had some time and threw this together. I think you'll learn more by looking at it and asking questions than me spoonfeeding it anyway.

1. The first diode is wired just to show that there's voltage?

Nope, D1 is used as reverse voltage protection. Even the most astute of us can reverse the power leads during hook-up after a long day. This prevents damage to the circuit in the event someone reverses the power leads, e.g., hooks + to - and vice versa. The only downside with adding a diode in this fashion is you'll lose about 0.7VDC going to the circuit. If you had a regulated 12.0VDC hooked up, then the circuit will only see about 11.3VDC. You have to factor this into choosing your resistor values for the LEDs - more on that later. Despite this, 12VDC from a car usually isn't regulated, so you're more likely to see 12.8-13.4VDC or so. In this case, the diode is also helping to drop the incoming voltage down to a value closer to 12VDC. D1 is a 1N4001. On the same note, C1 is used as a filter and should be rated 50VDC or higher to be safe.

2. SW1,2,and 3 I assume are switches like the ones SGT Wookie suggests? What about number 4? Is that just an NO switch?

Yes, SW1-SW3 are the mechanical BCD switches SgtWookie suggested. You have your choice of a thumbwheel or pushbutton. As SgtWookie mentioned, you'll want to be sure to get one cover. SW4 can either be a latching push button switch or a (non-momentary) toggle switch. I'd suggest the latter so you'll be able to "see" whether the one is on or off.

3. How will I know what resistors to use, as far as ohm and wattage?

Sorry, I meant to call out some of them. Excellent observation, especially on the wattage part - many people new to electronics forget about that. R1-R12 are 10kΩ, 1/4W. These are used as pull-down resistors because they "pull-down" the voltage going to input pins. These are used so that when the corresponding BCD pin is off, the IC knows the input is 0VDC, otherwise it will "float" and your display will do crazy things.

R13-R35 will depend on the displays used. We'll need to know if you're planning to build your own or use a pre-made display. The former will save a little money for the sizes you've mentioned and will require a lot more work, but you have more control and options as far as color and brightness. We'll travel this road once you're ready to tackle it.

4. Are there blank circuit boards available for me to assemble these components to?

There are a few options here. I first suggest you assemble the circuit on a breadboard and test it before soldering to a board. This will verify the schematic is correct and help you to easily fine-tune the brightness before you order enough parts for X boards.

Once past the breadboard and testing phase, you can:
1) Use pre-made generic PCBs such as: http://www.radioshack.com/product/index.jsp?productId=2102846 - not shown in the photo are the copper traces on the back that are identical to a breadboard. I like this one, but there are an assortment available.
2) Use a strip board such as: http://www.kpsec.freeuk.com/stripbd.htm - these are not real common in the U.S., but they work great. You use a Dremel or X-acto to cut strips as needed to make multiple traces.
3) Design your own board and either make it at home or send it off to get made professionally.

Between the three, I'd suggest option 2. Probably the best option in terms of time, labor, and cost for the quantities you've mentioned.

Before ordering parts, we need to hammer out what you'd like to do for the displays, DIY or pre-made? Also note most pre-made are designed for indoor use and may not be bright enough for daylight. Depends on who needs to "see" the display and how far away they are. You'll probably want to get or make a display and test that is bright enough and viewable before doing much with the circuit. Attached is a DIY display I did which shows the importance of having a filter. You can make these as simple or complex as you want.

 

No problem, I understand this a lot to digest. We normally have people do some research and propose solutions and help them along. As you're not doing this for a school assignment, need something quick, and intend to kinda go head-first into electronics with a project (one of my favorite approaches ), I had some time and threw this together. I think you'll learn more by looking at it and asking questions than me spoonfeeding it anyway.

That's pretty much how I roll! I tend to decide on a project and research it to death, then build it. I prefer to learn as I go, I seem to pick it up easier that way. A couple years ago I decided I wanted to learn to screen print, seemed like a better idea to do it myself than pay someone to do it. Same thing with embroidering, vinyl, etc. Sometimes I spend more, but at least I learn a new trade.

Nope, D1 is used as reverse voltage protection. Even the most astute of us can reverse the power leads during hook-up after a long day. This prevents damage to the circuit in the event someone reverses the power leads, e.g., hooks + to - and vice versa. The only downside with adding a diode in this fashion is you'll lose about 0.7VDC going to the circuit. If you had a regulated 12.0VDC hooked up, then the circuit will only see about 11.3VDC. You have to factor this into choosing your resistor values for the LEDs - more on that later. Despite this, 12VDC from a car usually isn't regulated, so you're more likely to see 12.8-13.4VDC or so. In this case, the diode is also helping to drop the incoming voltage down to a value closer to 12VDC. D1 is a 1N4001. On the same note, C1 is used as a filter and should be rated 50VDC or higher to be safe.

Ok I understand. I seen it in there, and wasn't quite sure why. I'm sure the car will provide more than 12vdc, most of the time it'll be closer to 14 as it does still have an alternator.

Yes, SW1-SW3 are the mechanical BCD switches SgtWookie suggested. You have your choice of a thumbwheel or pushbutton. As SgtWookie mentioned, you'll want to be sure to get one cover. SW4 can either be a latching push button switch or a (non-momentary) toggle switch. I'd suggest the latter so you'll be able to "see" whether the one is on or off.

Does each switch require endplates, or just 2 total for the 3 switches?

Sorry, I meant to call out some of them. Excellent observation, especially on the wattage part - many people new to electronics forget about that. R1-R12 are 10kΩ, 1/4W. These are used as pull-down resistors because they "pull-down" the voltage going to input pins. These are used so that when the corresponding BCD pin is off, the IC knows the input is 0VDC, otherwise it will "float" and your display will do crazy things.

R13-R35 will depend on the displays used. We'll need to know if you're planning to build your own or use a pre-made display. The former will save a little money for the sizes you've mentioned and will require a lot more work, but you have more control and options as far as color and brightness. We'll travel this road once you're ready to tackle it.

I think I'd like to build my own. I'd like control over brightness, and build as much as I can

There are a few options here. I first suggest you assemble the circuit on a breadboard and test it before soldering to a board. This will verify the schematic is correct and help you to easily fine-tune the brightness before you order enough parts for X boards.

Once past the breadboard and testing phase, you can:
1) Use pre-made generic PCBs such as: http://www.radioshack.com/product/index.jsp?productId=2102846 - not shown in the photo are the copper traces on the back that are identical to a breadboard. I like this one, but there are an assortment available.
2) Use a strip board such as: http://www.kpsec.freeuk.com/stripbd.htm - these are not real common in the U.S., but they work great. You use a Dremel or X-acto to cut strips as needed to make multiple traces.
3) Design your own board and either make it at home or send it off to get made professionally.

Between the three, I'd suggest option 2. Probably the best option in terms of time, labor, and cost for the quantities you've mentioned.

Before ordering parts, we need to hammer out what you'd like to do for the displays, DIY or pre-made? Also note most pre-made are designed for indoor use and may not be bright enough for daylight. Depends on who needs to "see" the display and how far away they are. You'll probably want to get or make a display and test that is bright enough and viewable before doing much with the circuit. Attached is a DIY display I did which shows the importance of having a filter. You can make these as simple or complex as you want.

Again, I really appreciate your help.Another question I have:The LEDs are clustered in the schematic. Would it have to be that way, or should it be more like this-8?

 

I'm sure the car will provide more than 12vdc, most of the time it'll be closer to 14 as it does still have an alternator.

We may need to take a different approach if the voltage varies much during operation. Any change in voltage with this design will be seen in the display. If the voltage fluctuates, the display brightness will fluctuate with it. Another good reason to breadboard it out first and test it before ordering too much.

Does each switch require endplates, or just 2 total for the 3 switches?

I *think* you just need one. Take a look at the datasheet for the one you're interested in. They appear to have one closed side and one open, presumably to attach to each other. So whether you need one or join twenty together, I believe you just need one cap for the last exposed end.

I think I'd like to build my own. I'd like control over brightness, and build as much as I can

In case that, I'd suggest cheap, bright LEDs. Ebay is one place and I've used ledshoppe.com. I suggest 5mm LEDs with a rating of 2000mcd or greater and about 30-45 degree viewing angle. Ledshoppe sells 10 degree viewing angle which is okay, but may not allow much viewing from the side. The 2000mcd will allow you to see it in daylight (reasonably anyway). You can purchase 1/8" PVC and drill holes to mount the LEDs or even plywood if you prefer.

The LEDs are clustered in the schematic. Would it have to be that way, or should it be more like this-8?

You are correct, I just drew it as shown to keep it simple. I've attached a revised schematic showing the position of each segment. Note the number of LEDs may change depending on the forward voltage of the LED you select (this is determined by the color). I'd suggest drawing out the layout of the 7-segments - you can use 1/4" circle as an approximate LED representation, although they are 5mm in reality. This will help you determine how far you want to space the LEDs from each other, how long the segments will be and ultimately how many LEDs you'll want per segment.

 

Now that I think of it, voltage shouldn't fluctuate, because I do run an alternator. On some of our other cars we don't. We basically charge between rounds, so there may be a slight voltage drop towards the end of a run. I'm thinking it may be minimal though.

It looks like I need to order some parts, and start playing around. Maybe the best starting point would be to draw out the LED segments as you suggest, and go from there. I'm thinking 4" for the height, and whatever the length winds up. You mentioned drilling pvc or plywood, in your pic of the display you made, what are they mounted to?

 

Now that I think of it, voltage shouldn't fluctuate, because I do run an alternator. On some of our other cars we don't. We basically charge between rounds, so there may be a slight voltage drop towards the end of a run. I'm thinking it may be minimal though.

Probably be okay then, you'll find out in the testing phase in any event.

You mentioned drilling pvc or plywood, in your pic of the display you made, what are they mounted to?

Personally, I like PVC. It's easy to machine and fairly durable. You can get it at McMaster or Enco.

McMaster: 8747K112

Enco (use-enco.com): 325-4530

I don't know if you use Enco much, but they offer free shipping for all orders over $99 this month with code: SEPUPS. Doubt you have that much in machining and hardware needs for other projects right now, but you never know.

Clear acrylic is cheap and works well, it just cracks easily and doesn't take impact well (dropping, getting hit with something, etc.). Clear polycarbonate would work well and is available at the big box hardware stores. You might need to paint the front a solid color so your digit doesn't look distorted though.

Bill M suggests plywood and it is certainly cheap. Having a little machining experience myself, I'm more comfortable with plastics and metals as they hold their shape better, afford greater machining precision, and you don't have to worry about effects from water contact, humidity or the like over time. You might use some 1/4" plywood scrap for some prototypes then use a stronger material for the finished product. While I love PVC, it ain't exactly cheap at $5+ a square foot.

Also, most LEDs have a very slight taper, so when selecting a drill bit, be sure to measure the diameter of the LED closest to the base (although not the lip of course).

If time allows, I'll try to sketch some simple LED 7-segment layouts and post them in the next day or two. If you want to go for more than one row of LEDs per segment, check this out: http://forum.allaboutcircuits.com/showpost.php?p=483972&postcount=75.

Not sure if that would be practical for 4" high displays, but it gives you some ideas about what you can do with displays.

 

Nobody has mentioned that the control section will need some small 7 segment LED displays and a whole 'nuther logic board, minus the switches, or can you put 2 driver chips on each BCD decoder?

 

Nobody has mentioned that the control section will need some small 7 segment LED displays and a whole 'nuther logic board, minus the switches, or can you put 2 driver chips on each BCD decoder?

I think that they are going to use the BCD Switches that have the number on them. Like this...

So the extra display would not be needed as you can see what number will be displayed.

 

That certainly is better than what I imagined!

 

Probably be okay then, you'll find out in the testing phase in any event.



Personally, I like PVC. It's easy to machine and fairly durable. You can get it at McMaster or Enco.

McMaster: 8747K112

Enco (use-enco.com): 325-4530

I don't know if you use Enco much, but they offer free shipping for all orders over $99 this month with code: SEPUPS. Doubt you have that much in machining and hardware needs for other projects right now, but you never know.

Clear acrylic is cheap and works well, it just cracks easily and doesn't take impact well (dropping, getting hit with something, etc.). Clear polycarbonate would work well and is available at the big box hardware stores. You might need to paint the front a solid color so your digit doesn't look distorted though.

Bill M suggests plywood and it is certainly cheap. Having a little machining experience myself, I'm more comfortable with plastics and metals as they hold their shape better, afford greater machining precision, and you don't have to worry about effects from water contact, humidity or the like over time. You might use some 1/4" plywood scrap for some prototypes then use a stronger material for the finished product. While I love PVC, it ain't exactly cheap at $5+ a square foot.

Also, most LEDs have a very slight taper, so when selecting a drill bit, be sure to measure the diameter of the LED closest to the base (although not the lip of course).

If time allows, I'll try to sketch some simple LED 7-segment layouts and post them in the next day or two. If you want to go for more than one row of LEDs per segment, check this out: http://forum.allaboutcircuits.com/showpost.php?p=483972&postcount=75.

Not sure if that would be practical for 4" high displays, but it gives you some ideas about what you can do with displays.

I believe I will stick to single row LED's. I don't want it to be too jumbled up. I'm thinking PVC will be my material of choice, although the testing phase may be done with whatever I have laying around the shop.

I'm getting anxious to start this, I laid awake almost all night last night thinking about it. Whenever I get an idea I have a hard time thinking about anything else. I have a pretty good idea of what needs to be done, now it's time to start doing it. First order is laying out the lights, and seeing how many I am going to need. I could just count the number they used in the one that's available, but I think I want to see it first hand, then build. Another question:What do you use as a filter??

 

Nobody has mentioned that the control section will need some small 7 segment LED displays and a whole 'nuther logic board, minus the switches, or can you put 2 driver chips on each BCD decoder?

I think that they are going to use the BCD Switches that have the number on them. Like this...

So the extra display would not be needed as you can see what number will be displayed.

It is my understanding that with these switches I would not need another display. However, down the line that may be something I venture into. I want to knock out a test piece first, run it on my car for a bit, and decide what I'd like to change. I may want that lit display in the car to be easily seen.

 

In case that, I'd suggest cheap, bright LEDs. Ebay is one place and I've used ledshoppe.com. I suggest 5mm LEDs with a rating of 2000mcd or greater and about 30-45 degree viewing angle. Ledshoppe sells 10 degree viewing angle which is okay, but may not allow much viewing from the side. The 2000mcd will allow you to see it in daylight (reasonably anyway). You can purchase 1/8" PVC and drill holes to mount the LEDs or even plywood if you prefer.

What is more important, viewing angle, or mcd??