LED indicating when the Disecq motor is running

[barney_555]

Anybody know an electronic circuit that could be used in-line between the receiver and the motor that could light a LED when the motor is running ?

It would be great when I switch from PAS9 to G10.

 

[Cascade]

In theory it wouldn't work because there's always 13/18V on the line.
In practice if you found a circuit that detected a slight drop (ie: when the motor's turning) that should work although it's more hassle than it's probably worth and wouldn't be that reliable.

 

[mark_calgary]

When the motor is running the current should be substantially higher.

You could detect the current change by measuring the voltage across a <small> series resistor. An op-amp or two for gain and threshold detection, a couple of inductors for RF isolation and you are away You could even power it all from the LNB supply.

Unfortunately construction of such a circuit (simple as the circuit may be) requires careful layout and testing to ensure that the integrity of the L-band signal (2+GHz) is not compromised and is not something you throw together with parts from Radio Shack (Or whatever it is now called up here in Canada).

It might be simpler to attach a position encoder to the dish somehow and just run some wires back to the receiver.

Or use a webcam pointed at the dish - likely somebody out there does this already.

 

[Cascade]

Mark, I was thinking about a voltage drop as opposed to current flow.

 

[barney_555]

I don't know, maybe reading the current by induction, like the inductive DC clamp meter.

 

[n4bbq]

Anybody know an electronic circuit that could be used in-line between the receiver and the motor that could light a LED when the motor is running ?

Bonjour,

J'aime la France. Elle est belle. J'étais là en avril. Parlons de l'électronique.

The circuit below should work.

C1 is a bypass capacitor for the RF. L1 and L2 and inductors that will pass the DC but block the RF. R1 is a very low resistance resistor and R2 is a current-limiter to the LED.

As the current increases in the coax, the voltage drop across R1 will increase and cause the LED to emit. You will need to adjust the values of R1 and R2 to get a decent burn, but this should work ok.

You will also be inducing a bit of loss in the line, but if you keep your leads short and build it small enough, I doubt you'll ever notice it.

 

[barney_555]

Thank you for the fast response

Désolé, je ne connais pas la France, je suis Québécois.

I don't know if i'm right but : V=RI, so 0.1ohm * 500mA = 0.05V and it takes 1.5V to light a Led, I believe.

Maybe I'm wrong, those theory are far away in my mind, let me know.

 

[mark_calgary]

Thank you for the fast response

Désolé, je ne connais pas la France, je suis Québécois.

I don't know if i'm right but : V=RI, so 0.1ohm * 500mA = 0.05V and it takes 1.5V to light a Led, I believe.

Maybe I'm wrong, those theory are far away in my mind, let me know.

You are right, which is why you need to take that small voltage and amplify it. If you detect the change in voltage acoss R1 between motor off and on and then turn the LED on above a predetermined threshold voltage you will have a motor moving indicator.

 

[barney_555]

Hi Mark. Do you think it's practical or possible to do given the hi frequency of the sat signals ? I don't want something that will interfere with my signal.

 

[mark_calgary]

Hi Mark. Do you think it's practical or possible to do given the hi frequency of the sat signals ? I don't want something that will interfere with my signal.

Given access to the right tools, and with experience in RF design or tinkering (such as ham radio experimentation) it is a "simple" project. The key is in the circuit board layout. Impedance mismatches between the cable and the circuit will cause losses.

If you do a search on the internet you may find where people have posted details of electronic projects they have done. You'll get an idea about what is involved in terms of construction for something that involves 1-2GHz signals.

The component costs are not that high. It will be the time commitment which has the higher price.

Are you thinking of constructing such a circuit? If so keep us informed.

 

[n4bbq]

Désolé, je ne connais pas la France, je suis Québécois.

Désolé! Je n'ai jamais été au Canada, mais je veux aller.

I don't know if i'm right but : V=RI, so 0.1ohm * 500mA = 0.05V and it takes 1.5V to light a Led, I believe.

Maybe I'm wrong, those theory are far away in my mind, let me know.

Correct, that is why you will need to try different values for R1, but don't get too high a value or your motor may not operate properly. Besides, I am betting the motor may pull more than 500 mils, but I'm not sure. I was thinking more in the range of an one amp or more.

I may scratch one together just for kicks and see what values to use, but I have a different motor than you do.

Also you want to choose L1 and L2 with the current capacity of at least thee times the total circuit current to be sure they don't go up in smoke.



NOTE: I just looked at my motor's specs and it only pulls in the range of 150 mils!

In this case, you may have to add a transistor to turn on an LED supplied by the normal drive voltage. I'll re-draw the schematic tonight if I get time and upload that. I'd really like to build one forst to see if I could get it to work like this though....

 

[cralt]

Sounds like alot of work...


Why not just use a signal meter set to read LNB currrent?

When the motor moves the current goes up.....

Even my cheap-o Sat Buddy can read LNB current.

 

[Cascade]

Don't knock the SSM22! they're fantastic meters

 

[cralt]

Don't knock the SSM22! they're fantastic meters

Wasnt knocking it...

I was talking about another meter I have called a Sat Buddy. Its small and only really works right for DBS stuff. But they can take a beating like nothing else.

SSM22's are nice but drop them off a roof once or twice and they are all done

 

[mark_calgary]

Sounds like alot of work...

I certainly won't disagree with you there.

 

[n4bbq]

Sounds like alot of work...

Depends on what you consider work.

Funny, a neighbor told me the same thing about installing my motorized Ku setup when all he had to do was set up a fixed dish for Direct TV...

 

[spindoctor]

well these people got it way before


LED

LNB TOO

http://stores.yahoo.com/hightech/stdvbrecsupp.html