- Joined
- Apr 1, 2011
- Messages
- 15,181
- Helped
- 2,899
- Reputation
- 5,810
- Reaction score
- 2,982
- Trophy points
- 1,393
- Location
- Minneapolis, Minnesota, USA
- Activity points
- 113,727
That is correct.
You show the thumbwheel switch as having four connections, there are actually five because one is common to the four others.
The problem with driver ICs like the 4511 is if you leave an input pin disconnected (such as would happen if its switch contact was open) it can randomly be high or low and you see random flickering digits. The resistors to ground (we call them "pull-down" resistors) make sure the pin is at zero volts unless the switch closes and connects it to +5V, it is always in one or the other state.
I would suggest 47K resistors for the pull-downs.
I suggest 330 Ohms if you use a 5V supply and 680 Ohms if you use a 12V supply. The maximum voltage allowed is 15V.
two 9 Volts presumably in parallel?
Glad I made someones day!Brian, just to hear you say that I said or did something correctly gives me hope that I can do this.
That type of switch is available in several variations. Some have 0-9 (decimal) and some have 0-15 (hexadecimal), the difference is in how many 'positions' or selections it is possible to make. In most electronic applications we use hexadecimal because it is more efficient but for the numbers 0-9 they are both the same. The reason is that each switch has one common side and four open/close sides, it is effectively four switches in one module that all operate together as the switch is turned. Don't confuse this with four digits, these are four BITs on one digit. The switches open and close in different combinations according to the number you selected and these can be read as a short through the contacts from the common to switched connections. Think of it is four toggle switches, all linked at one end but turning on an off in different combinations as each number is selected. In reality of course the toggle switches are part of one rotary mechanism. If you consider the open and closed combinations as '1' or '0' in binary, you can see that the selected position number produces the equivalent binary number on the switches. That's why the 4511 can decode the binary number back to a decimal digit. Going back to decimal and hexadecimal, you may have noticed that 0 to 9 doesn't use all the available combinations and there are in fact 16 different combinations of four bits:My switch does have a 5th connection with a soldered rod running through all 4 switches. I guess that's what you're referring to?
Yes, the LE pin latches the number on the input pins. I laymans terms, it captures and snapshots and freezes the number so even if you change the input bits, the displayed digit stays the same. Operating the latch a second time will update with the number on the input pins at that time again. We use the LE normally so that counting processes are not seen 'live' on the digits and only the result is shown.With the 47K resistors, will I be able to use a toggle switch to turn the 7-Segments on and simultaneously activate the Latch Pin to show the number that was just dialed into the thumbwheel?
I would be inclined to follow the advice already given. LEDs are fairly hungry in terms of the current they need so a substantial battery is advised. The voltage isn't critical but small batteries will drain very fast (a few minutes). If you can use a larger holder with several 'A' size batteries or bigger in series it will last much longer.What about doing it the way the actual prop is wired: two 9 Volts presumably in parallel?
Hi,
It looks like the breadboard power strip at the bottom needs + and -. you may have inadvertently crossed wiring somehow, therefore the dimly lit unused segments.
The edge blue and red stripes are to indicate negative and positive rails but they are not joined from side to side. You need to link the two blue ones and link the two red ones! Otherwise it looks OK. Yes, the latch needs to be fired to 'lock' the digit selected on the thumbwheel into the 4511 or it will show a random digit at start-up.
Brian.
Hi,
I just told you. Put a wire from the red one to the other red one, and a black one from the blue strip to the other blue strip.
GOT IT!!!
I re-read Brian's last post, and EVERYTHING on the bottom had to be ported over to the top. Looks great!!!
I think it should simultaneously activate the 4511 latch so a specific 4-digit number displays on that readout. Is there a memory dump on a 4511 so I change a number already assigned to a display, or would the toggle in the OFF position reset it?
Also, there is a spring loaded momentary switch on the left side of the case. This button is clearly depressed when the case is closed, and extended when the case is open. There are two wires that run to it from the two 9 volts, so I'm guessing it’s the ON/OFF switch for everything and functions like a refrigerator light switch. I think I can wire this with an input from the batteries to a 12 pole terminal block going to each of the 12 circuits. Sound right?
That's where you can use the 'BI' pin on the 4511 ICS. BI is "Blanking Input", normally used to turn the digit off completely when, for example, you don't want leading zero digits in a number. If you join all the BI pins together you can use them like a master on/off switch for the display but without turning the IC itself off. Add a pull-up resistor between the supply ando the BI pins and wire the case switch between BI and ground. Grounding BI makes the display turn off. If it works in reverse, wire the resistor to ground and the switch to supply instead.I'm beginning to suspect that only the led displays were turned off and on while shooting the scene. After turning on the latch IC's, they stayed on so that each IC retained its number.
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?