BCD switch..... more

Moderators: George Geddes, David Martin, dave robinson, Iain Purdon, ecca

BCD switch..... more

Postby ecca » Tue Nov 20, 2012 4:18 pm

I found one at RS with 10 positions,327-939, stoppable downable (eh?) to 8.
There are good things and bad things about it but it's the only one I've found with 8 positions. ( apart from a monster industrial one that even blind man Robbo couldn't fail to see)
I don't like those hexadecimal switches.
It's not too expensive at around £5.
It's compact.
But......... it's a PCB mount type which means its connections are a bit weedy. I got round this by mounting it into a piece of veroboard.
It has 14 connections from A to N and the data sheet that you can download is complete gobbledegook. It's also wrong so I had to do a truth table on it last night and here are the connections if anyone wants to use it.
The switch connection D goes to the etap bcd connection A ( S0)
Conn. B goes to etap B (S1)
Conn . I goes to etap C (S2)
Link EFGLMN for the common connection.
Hope it helps someone.
Cheers
Ecca
User avatar
ecca
 
Posts: 3554
Joined: Sat Sep 12, 2009 7:25 pm
Location: Finca de Pelsall
Full Real Name: Eric Blossom Thacker

Re: BCD switch..... more

Postby dave robinson » Tue Nov 20, 2012 5:14 pm

KNOBS ! :lol:
Dave Robinson
User avatar
dave robinson
 
Posts: 5453
Joined: Wed Sep 09, 2009 1:34 pm
Location: Sheffield
Full Real Name: David Robinson

Re: BCD switch..... more

Postby ecca » Tue Nov 20, 2012 5:35 pm

BIG KNOB
User avatar
ecca
 
Posts: 3554
Joined: Sat Sep 12, 2009 7:25 pm
Location: Finca de Pelsall
Full Real Name: Eric Blossom Thacker

Re: BCD switch..... more

Postby dave robinson » Tue Nov 20, 2012 5:38 pm

ecca wrote:BIG KNOB



You been on the other site Ecca . . . . . ? :lol:
Dave Robinson
User avatar
dave robinson
 
Posts: 5453
Joined: Wed Sep 09, 2009 1:34 pm
Location: Sheffield
Full Real Name: David Robinson

Re: BCD switch..... more

Postby Mark Burton » Wed Dec 12, 2012 2:22 pm

Could you use a CMOS 4511 to drive a 7-segment display directly using the BCD output from the rotary switch? That way it would avoid the issues of markings for the rotary switch and the drawbacks of the small thumb thingy - and more importantly would be very easy to see on stage etc

or am I barking?
Mark Burton
User avatar
Mark Burton
 
Posts: 365
Joined: Thu Sep 17, 2009 9:18 am
Full Real Name: Mark Burton

Re: BCD switch..... more

Postby ecca » Wed Dec 12, 2012 2:44 pm

Certainly could Mark.
One problem would be that the voltage coming from the BCD switch is 3.3 which is low to be running CMOS.
It's also not as simple as it looks.........
User avatar
ecca
 
Posts: 3554
Joined: Sat Sep 12, 2009 7:25 pm
Location: Finca de Pelsall
Full Real Name: Eric Blossom Thacker

Re: BCD switch..... more

Postby Mark Burton » Wed Dec 12, 2012 4:14 pm

You could use a pair of trannies :shock:

Or use a 74LS48 which will cope better with the lower voltage.

How easy is it to mount a 7SD on a front panel? Would it need to be behind some kind of lens??
Mark Burton
User avatar
Mark Burton
 
Posts: 365
Joined: Thu Sep 17, 2009 9:18 am
Full Real Name: Mark Burton

Re: BCD switch..... more

Postby ecca » Wed Dec 12, 2012 4:48 pm

Use a pair of trannies for what ?

Low power TTl is actually worse than CMOS with regard to supply voltage. It runs at 5 volts nominal, 4.75 min.
CMOS, in theory runs at 3 to 15 volts but it's not recommended at that low a voltage.

You would also have to consider just how much power is available from the 3.3volt supply, it being derived from the daughterboard.

If voltage translators or opto isolators are used to get away from the 3.3 volt problems then a 7805 regulator will have to be run from the incoming 12 volts and frankly, you've started to spend money and get it's getting a bit messy.

The display would have to be mounted in a bezel.
User avatar
ecca
 
Posts: 3554
Joined: Sat Sep 12, 2009 7:25 pm
Location: Finca de Pelsall
Full Real Name: Eric Blossom Thacker

Re: BCD switch..... more

Postby Mark Burton » Wed Dec 12, 2012 5:55 pm

sorry - misunderstood :oops:

Had assumed (yes - bad move) that it ran on a 5v supply - but for some reason there was only 3.3v off the selector switch and I thought you meant that 3.3 was too low to register as a "high" on a CMOS chip (hence the pair of trannies to use the 3.3v to get a 5v switch onto the input of the 4511).

I've ordered my kit and will probably have a go in the new year, and if I feel brave might try the 7SD :-)
Mark Burton
User avatar
Mark Burton
 
Posts: 365
Joined: Thu Sep 17, 2009 9:18 am
Full Real Name: Mark Burton

Re: BCD switch..... more

Postby RogerCook » Thu Dec 13, 2012 1:14 am

Interesting post on Piet's blog regarding the automation currrently under development and which may help with the display issue

http://www.echotapper.nl/wp/

Roger
RogerCook
 
Posts: 452
Joined: Thu Sep 17, 2009 8:56 am
Full Real Name: Roger Cook

Next

Return to Parts List and Where to get them...

Who is online

Users browsing this forum: No registered users and 1 guest

Ads by Google
These advertisements are selected and placed by Google to assist with the cost of site maintenance.
ShadowMusic is not responsible for the content of external advertisements.