A/D's and LED decoder/drivers
A/D's and LED decoder/drivers
(OP)
List,
First let me say hello as I am new to this.
I'm trying to display a YIG tuned filter's tuned frequency(2-18Ghz) as a product of the control voltage (0-10V). The problem is I need 6-digits (7-segment led's) to get the resolution I want. I guess I will need at least a 24-bit A/D and an LED decoder/driver that will interface the LED's. I also want this to be stand-alone, not microprocessor controlled. All I can find so far are mux led decoder/drivers that will do the job. Also, all I can find are serial A/D's that are at least 24-bit. Is there any way I can use two 12-bit A/D's? I need parallel operation for this to be stand-alone don't I? I know the wiring will get complex but like my ID states, I'm basically an analog man. I don't have the capability at work to program chips. Any help will be greatly appreciated.
First let me say hello as I am new to this.
I'm trying to display a YIG tuned filter's tuned frequency(2-18Ghz) as a product of the control voltage (0-10V). The problem is I need 6-digits (7-segment led's) to get the resolution I want. I guess I will need at least a 24-bit A/D and an LED decoder/driver that will interface the LED's. I also want this to be stand-alone, not microprocessor controlled. All I can find so far are mux led decoder/drivers that will do the job. Also, all I can find are serial A/D's that are at least 24-bit. Is there any way I can use two 12-bit A/D's? I need parallel operation for this to be stand-alone don't I? I know the wiring will get complex but like my ID states, I'm basically an analog man. I don't have the capability at work to program chips. Any help will be greatly appreciated.





RE: A/D's and LED decoder/drivers
If this is a one of-a-kind for you to use, just by an HP voltmeter $800 and be done with it.
If this is for production you really should use micro. You can get some very inexpensive development tools that will
get you good results.
Even if you were to do some sort of strange venier scheme to get two A/Ds to work together you'd still want a micro to supervise everything.
Keith Cress
Flamin Systems, Inc.- <http://www.flaminsystems.com> - kcress@<solve this puzzle>
RE: A/D's and LED decoder/drivers
Can't even see how you are controlling the frequency to 1 ppm without digital controls. And if you have digital controls, you should drive your display directly from the digital
TTFN
RE: A/D's and LED decoder/drivers
Dan
Owner
http://www.Hi-TecDesigns.com
RE: A/D's and LED decoder/drivers
RE: A/D's and LED decoder/drivers
RE: A/D's and LED decoder/drivers
So, the answer is: Yes, it is possible. Probably somewhere out there in a app note or design idea such a circuit exists probably for pressure sensor linearization. The engineer who designed that circuit frequently sourced the circuits from published sources.
However, 24 bits is another issue, unless you are throwing away the last 8 bits.
RE: A/D's and LED decoder/drivers
RE: A/D's and LED decoder/drivers
Why are you not using a frequency counter? If you're tuning a frequency, why not measure the frequency instead of some "equivalent?" There are just so many error sources to account for that your ultimate accuracy is probably no better than 0.1% Just your voltage scaling error alone...
As for A/D, there are >20-bit devices out there:
http://www.aldinc.com/pdf/mb1s.pdf, a 5 1/2 digit DVM chip
http://www.chipcatalog.com/Cat/279.htm
http://w
TTFN
RE: A/D's and LED decoder/drivers
RE: A/D's and LED decoder/drivers
Part of engineering the appropriate engineering solution is analysis of alternatives. If you are unwilling to entertain alternatives, then you do your company a disservice, particularly if the resultant product may be more widely useable, more accurate, and has NIST-calibration traceability potential.
TTFN
RE: A/D's and LED decoder/drivers
RE: A/D's and LED decoder/drivers
Had you been up front about the purpose of your project, you wouldn't have gotten half the responses that you did.
TTFN
RE: A/D's and LED decoder/drivers
RE: A/D's and LED decoder/drivers
Would that help?
RE: A/D's and LED decoder/drivers
If I understand correctly, you want to take 1V and A/D
convert to 24 bits. That means resolution of 1/16.7 million which is basically microvolts level. This is down in the noise. Most of your resolution would be wasted on noise.
You might want to amplify it up so that you can get out of the "noise floor" and use more of the resolution.
Say, you succeeded.
If you are not a digital guy [I understand] and don't want to use a micro, the next thing you can do is to use discrete logic to build a decoder that will take the ADC output and translate that to a 6 digit number to be displayed. You'll need the decoder to translate the number to those 7-segment LED drivers, which will display it.
Good luck--it can be done, the challenges will: get out of the noise floor, and then that decoder circuit.
RE: A/D's and LED decoder/drivers
It's not that you are incompetent or lacking the will.. It is just horrendously hard. It is on the level with walking to the moon. It ain't gonna happen and isn't even going to come close to happening. I'm sorry. The best you can hope for is to buy or assign an expensive piece of equipment to it and then you will only get near not close to the indication you desire.
Keith Cress
Flamin Systems, Inc.- <http://www.flaminsystems.com> - kcress@<solve this puzzle>
RE: A/D's and LED decoder/drivers
I need to ask if you have ever tried to make an error budget for what you are about to do?
First, there is noise (OK, you can filter that down to ridiculuously low levels - but that will mean measuring for very long time).
Second, you have thermal drift. Given the environment you are telling us that you have (home lab), I cannot imagine that you can keep temperature within a few tenths of a degree (F or C), which would be required not to have problems with the conducting and soldering materiels at hand for someone working at home.
Then, there are all kinds of external electric influences. Mostly radio and TV transmitters, but also CB, pagers, PLC (Power Line Communication), radar and lots of such stuff. I guess that the oscillator you work with also outpts its share of radiation.
So, if you divide your error budget fair between these you will have around 1/4 of your accuracy lost in each of them. That effectively rises resolution and accuracy demand another two bits or so.
As most poster say: It is the wrong way to go. It cannot be done.
We do not say that to put you down, but to help you (from hurting yourself, perhaps). If you study these fora, you will find that the tone is kind and polite. We have rules that allow us to keep it that way and I find your childish reaction ("I came here, to get suggestions or advice on the circuit I want to build, not the one YOU want to build. I can see there are too many people here looking down on me from atop their high horses though... sorry I asked.") very diverging, to say the least.
We are seasoned designers from all walks of life and technology that gather to share insights and help each other and others. You included. But we do not accept flames as soon as things don't go your way. Ever worked in a lab? Ever got advice from someone that knew the stuff better than you? Did you accept it or did you tell that guy to shut up? Just asking...
Gunnar Englund
www.gke.org
RE: A/D's and LED decoder/drivers
I tried to help you but...it only brought in more reasons not to do it your way.
The gents are correct in that you would not achieve good results. The alternatives suggested are much easier, quicker and cheaper.