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currydon(at)bellsouth.net
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 Posted: Tue Dec 30, 2008 12:48 pm Post subject: EI Altitude Clock Mod |
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Ok all you electronics warriors out there, here’s a good one: Electronics International designed and markets a pretty nifty-looking aircraft clock called the ASC-5A. One of the nifty things about it is that it is more than just a clock – it’s also an altitude alerter. Put in your MDA and your speed-based approach time, and you’ll get an LED indication on the face of the instrument telling you that you have arrived either at your altitude or your time. It even has an external-warning capability that, when paired with a tone or voice generator, can send alerts to your headset. But here’s the rub: it only has ONE external-warning wire, so regardless of whether it is a timer alert or an altitude alert, it goes out over this one wire (and in the same way, probably as a ground). As a result, when your headset alert sounds on a VOR approach, you must obtain additional input (i.e., you need to look at the face of the clock or your altimeter) to determine whether it is because you have reached the MDA and you need to level off or because you have exhausted your time and need to execute a missed approach. So, internally the unit can differentiate between altitude events and timer events because it lights different LEDs on the face of the instrument for these different events, but EI didn’t extend that basic capability to the external-warning feature sticking out the back of the instrument. What were they thinking? At this point, it seems like a simple matter to tap into the light circuits that activate the LEDs on the front of the instrument, extend some wires from those taps out the back, hook up a tone or voice generator, and receive separate signals in your headset for time and altitude alerts. But I don’t want to open mine up without first getting some feedback. Ok, I soldered once and it didn’t turn out well, so I’m reluctant to tear into my ~$500 instrument without lots of encouragement (I’ve learned that things that begin with, “Honey, watch this!” often don’t turn out well. . .)! Any thoughts?
Thanks,
Don
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Ed Anderson
Joined: 10 Jan 2006
Posts: 475
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| Posted: Tue Dec 30, 2008 5:13 pm Post subject: EI Altitude Clock Mod |
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In electronics all things are possible, Don (well, almost {:>)).
The feasibility of doing what you suggest is certainly conceptually simple; however, it depends quite a bit on what format the electronics have taken. If there are isolated wires running from a board to a couple of LED holders then that would probably be fairly simply provided you take care not to overload load the LED circuit. I would put in some sort of isolation barrier – such as an Ops amp – perhaps an Ops amp circuit with a tone generator designed in.
However, if the LED’s are an integrated part of a printed circuit board - then while still conceptually feasible, you need someone who knows how to modify a board (probably with surface mount components) - a person with the right skills and experience could do it – but, where do you find him? I certainly would hesitate to let just anyone wearing a hat with a lightening bolt through it tackle it.
If you can do it without damage to the unit, you might open it up and take a peek. If it looks like wires to the LEDs, then you might consider proceeding further – if it looks like the LED’s are an integrated part of a print circuit board, I think I would just button it back up.
I agree with you that one would have thought the designer/manufacture would have considered the advantages of a dual audio alarm.
Good luck
Ed
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson(at)carolina.rr.com
http://www.andersonee.com
http://members.cox.net/rogersda/rotary/configs.htm#N494BW
http://www.dmack.net/mazda/index.html
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Don Curry
Sent: Tuesday, December 30, 2008 3:45 PM
To: aeroelectric-list(at)matronics.com
Subject: EI Altitude Clock Mod
Ok all you electronics warriors out there, here’s a good one: Electronics International designed and markets a pretty nifty-looking aircraft clock called the ASC-5A. One of the nifty things about it is that it is more than just a clock – it’s also an altitude alerter. Put in your MDA and your speed-based approach time, and you’ll get an LED indication on the face of the instrument telling you that you have arrived either at your altitude or your time. It even has an external-warning capability that, when paired with a tone or voice generator, can send alerts to your headset. But here’s the rub: it only has ONE external-warning wire, so regardless of whether it is a timer alert or an altitude alert, it goes out over this one wire (and in the same way, probably as a ground). As a result, when your headset alert sounds on a VOR approach, you must obtain additional input (i.e., you need to look at the face of the clock or your altimeter) to determine whether it is because you have reached the MDA and you need to level off or because you have exhausted your time and need to execute a missed approach. So, internally the unit can differentiate between altitude events and timer events because it lights different LEDs on the face of the instrument for these different events, but EI didn’t extend that basic capability to the external-warning feature sticking out the back of the instrument. What were they thinking? At this point, it seems like a simple matter to tap into the light circuits that activate the LEDs on the front of the instrument, extend some wires from those taps out the back, hook up a tone or voice generator, and receive separate signals in your headset for time and altitude alerts. But I don’t want to open mine up without first getting some feedback. Ok, I soldered once and it didn’t turn out well, so I’m reluctant to tear into my ~$500 instrument without lots of encouragement (I’ve learned that things that begin with, “Honey, watch this!” often don’t turn out well. . .)! Any thoughts?
Thanks,
Don
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currydon(at)bellsouth.net
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| Posted: Tue Dec 30, 2008 5:33 pm Post subject: EI Altitude Clock Mod |
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simon(at)synchdes.com
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| Posted: Tue Dec 30, 2008 7:36 pm Post subject: EI Altitude Clock Mod |
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Don, I looked at the ASC-5A Operating Instructions and saw a picture of its front panel. I am willing to bet that all of those LEDs, the LCD and the switches are connected directly to a printed circuit board. You can verify this for us by opening the unit and looking at it. Obviously, you do this at your own risk.
Regardless of whether they are connected by wire or printed circuit board, you can connect to these LEDs by wire. All you have to do is solder wires to the solder points. I’d suggest that you have this done by a person known as an “assembler” in the electronics world. I’ve seen too many engineers who think they know how to solder, only to destroy a board by applying too much heat, too little heat, too much solder, not cleaning flux off the board, etc. A poor solder job usually results in a failure in our vibration environment.
Typically, an LED will be turned on by a driver going low at its cathode. This causes it to sink current through the LED. The LED’s anode is connected to the voltage source through a current limiting resistor. When the LED is turned off, the driver will be in the tri-state mode, thus causing only leakage current to flow through the LED. Therefore, when turned on, the LED’s cathode will be low, and when turned off, the LED’s cathode will be high. What “low” and “high” is depends on the driver and voltage source used.
Since a low most likely is the active state (you can verify this), it is not good enough by itself to generate a tone. This means that you will use it as a gating signal to generate such a tone. Someone earlier suggested that you will have to use op amps to isolate these two signals so that they don’t interfere with the LEDs’ operation. I would suggest keeping it in the digital world and using an appropriate driver that also has a high input impedance. In either case, you are now faced with bringing out one or two ground wire(s) with these two wires and running all wires to wherever you are taking them to, because you will need a reference ground where you are going. I will suggest that you write me directly after you find out what’s inside your ASC-5A if you are really serious about this project. There are several details that need to be known to find the best course of action, and only the owner can determine these details.
Simon Ramirez
Copyright 2008
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Don Curry
Sent: Tuesday, December 30, 2008 3:45 PM
To: aeroelectric-list(at)matronics.com
Subject: EI Altitude Clock Mod
Ok all you electronics warriors out there, here’s a good one: Electronics International designed and markets a pretty nifty-looking aircraft clock called the ASC-5A. One of the nifty things about it is that it is more than just a clock – it’s also an altitude alerter. Put in your MDA and your speed-based approach time, and you’ll get an LED indication on the face of the instrument telling you that you have arrived either at your altitude or your time. It even has an external-warning capability that, when paired with a tone or voice generator, can send alerts to your headset. But here’s the rub: it only has ONE external-warning wire, so regardless of whether it is a timer alert or an altitude alert, it goes out over this one wire (and in the same way, probably as a ground). As a result, when your headset alert sounds on a VOR approach, you must obtain additional input (i.e., you need to look at the face of the clock or your altimeter) to determine whether it is because you have reached the MDA and you need to level off or because you have exhausted your time and need to execute a missed approach. So, internally the unit can differentiate between altitude events and timer events because it lights different LEDs on the face of the instrument for these different events, but EI didn’t extend that basic capability to the external-warning feature sticking out the back of the instrument. What were they thinking? At this point, it seems like a simple matter to tap into the light circuits that activate the LEDs on the front of the instrument, extend some wires from those taps out the back, hook up a tone or voice generator, and receive separate signals in your headset for time and altitude alerts. But I don’t want to open mine up without first getting some feedback. Ok, I soldered once and it didn’t turn out well, so I’m reluctant to tear into my ~$500 instrument without lots of encouragement (I’ve learned that things that begin with, “Honey, watch this!” often don’t turn out well. . .)! Any thoughts?
Thanks,
Don
[quote] [b]
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