analog vrs digital

rdmmdr · 9th April 2007, 03:50

Those of us that feel brave enough or stupid enough to design our own electronics, have pondered the analog vrs digital debate. And after several recent posts i decided it was time to put my two cents in.

Analog is a good system if you only want to display o2 levels. while it was used successfully in the Mk/16 series for control. It does not have the adaptive ability that digital control provides. As Kevin, the master of the Mk/16 series, has pointed out.

So how does one go about designing their own electronics, or why do we? For the why, it is either an issue of funds or an issue of trust. Some of us cannot afford a new HH, and some of us don't trust the current electronics out there. Why you decide to build your own, is not as important, as what you what them to do.

Rebreather electronics fall in to several categories.

1. single cell o2 meters for the dolphin and kiss units for an example
2. triple cell o2 such a Martin's

both of these are good examples of analog design that has a long history of service. And a known track record.

3. triple cell digital to a single display
4. triple cell digital to a single display with control
5. and a HUD to any of the above units.

for examples one and two, it is not worth the effort to re-engineer the systems it has been done so many times and the equipment is available commercially. But if you want to we will be happy to help.

For the digital world, we get in to all kinds of problems. Can you design the hardware?. Can you design the software? What do we what it to do? Do we want to use an adaptive injection algorithm like Kevin? how much data do we want to display at one time? Do we use a 4x20 or an 2x8 display? What are we going to use a an interface? magnets ? tap? How do we do setpoint changes? Do we include deco?

So what are the minimum requirements of a digital controller?
1. o2 cells, to provide the data in.
2. op amp to make that data usable for the pic.
3. pic to decide what you are going to do with that data.
4. display
5. output/ solenoid or HUD.

design parameters

Every systems need to be redundant. We use three cells to insure that, but we tolerate linked controllers ,IE two masters at the same time. The kiss principal needs to be in-place, one controller= one handset and the solenoid. other controller = HUD and handset.

i suggest the use of four cells, two for one unit and one channel from the other unit for the third. we can establish 100% isolation from one controller to the other in the cells, and still have three cell voting logic available. The basic principle is that one failure will not effect the next problem. One handset fails,what happens next? This is not included in the current designs. I want a rebreather that will not try to kill me if it has a battery problem, software lock up. That is why i build my own electronics.

rick m

cstmwrks · 9th April 2007, 17:00

Quote: (Originally Posted by rdmmdr)

Those of us that feel brave enough or stupid enough to design our own electronics, have pondered the analog vrs digital debate. And after several recent posts i decided it was time to put my two cents in.

rick m

Great input.. I suspect mine was one of those recent posts.
When I made my LM 3914 post I never made it real clear my motavation.
I'm not on the analog side per say. It is pretty much a fact that digital offers so much more. But that is not my interest. I'm out to come up with a simple analog no frills contoller with voting ability. I do not need deco, I do not need set point adjustment on the fly. I do want an override control.. known as the off switch.

Though this is spilling the beans I'm more intersted in building an electrolung clone for no other real reason than to do it. To be as true to the electrolung design as posseble the electronics will be analog. Though I stopped posting about it on any forums the DIY polarographic sensor project has not been forgoten.

**jmurba** · 9th April 2007, 20:42

Quote: (Originally Posted by rdmmdr)

Those of us that feel brave enough or stupid enough to design our own electronics, have pondered the analog vrs digital debate. And after several recent posts i decided it was time to put my two cents in.

Analog is a good system if you only want to display o2 levels. while it was used successfully in the Mk/16 series for control. It does not have the adaptive ability that digital control provides. As Kevin, the master of the Mk/16 series, has pointed out.

So how does one go about designing their own electronics, or why do we? For the why, it is either an issue of funds or an issue of trust. Some of us cannot afford a new HH, and some of us don't trust the current electronics out there. Why you decide to build your own, is not as important, as what you what them to do.

Rebreather electronics fall in to several categories.

1. single cell o2 meters for the dolphin and kiss units for an example
2. triple cell o2 such a Martin's

both of these are good examples of analog design that has a long history of service. And a known track record.

3. triple cell digital to a single display
4. triple cell digital to a single display with control
5. and a HUD to any of the above units.

for examples one and two, it is not worth the effort to re-engineer the systems it has been done so many times and the equipment is available commercially. But if you want to we will be happy to help.

For the digital world, we get in to all kinds of problems. Can you design the hardware?. Can you design the software? What do we what it to do? Do we want to use an adaptive injection algorithm like Kevin? how much data do we want to display at one time? Do we use a 4x20 or an 2x8 display? What are we going to use a an interface? magnets ? tap? How do we do setpoint changes? Do we include deco?

So what are the minimum requirements of a digital controller?
1. o2 cells, to provide the data in.
2. op amp to make that data usable for the pic.
3. pic to decide what you are going to do with that data.
4. display
5. output/ solenoid or HUD.

design parameters

Every systems need to be redundant. We use three cells to insure that, but we tolerate linked controllers ,IE two masters at the same time. The kiss principal needs to be in-place, one controller= one handset and the solenoid. other controller = HUD and handset.

i suggest the use of four cells, two for one unit and one channel from the other unit for the third. we can establish 100% isolation from one controller to the other in the cells, and still have three cell voting logic available. The basic principle is that one failure will not effect the next problem. One handset fails,what happens next? This is not included in the current designs. I want a rebreather that will not try to kill me if it has a battery problem, software lock up. That is why i build my own electronics.

rick m

Hi Rick,

as for the reasons to design a digital circuit there are loads of, but the first for me is to be able to built a couple of gauges to be able to always get one to dive.
could afford a HH or any other electronics but I could not afford 3 or 4 gauges (((-:
I did 5 digital gauges.
the second reason is to get exactly what I you need, I need a triple gauges, needed a really audible alarm, I needed a flexible system I could add a hud to without modifying the circuit... I have it.
the third reason is the possibility to write and adapt the program... the heart of the system is the program.
the fourth is to be sure to be able to repair or built an other circuit in 7 days max...

my technical choices were:

-Op amp analog devices op490 (quaduple)
-Fixed amp op gain (no anlaog calibration)
-amplification filtration
-Lm 385 2.5v tension ref
-16F876 microchip microcotroller, mabye one of the most produced one (there are millions of everywhere), it s well knonw, not new , no surprise, it's programmation is also something really known and mastered.
- 2x16 LCD display
-5,4 volts supply (6 volts minus the diode)
-proton + compiler
- no mix between gauge program and deco program (after many hesitations (((-

Simplicity was my main strain, classic analog components one can buy throught rs or farnell, hyper classic microcontroller...

here is it at the low part of the page : Jean Michel Urbani Kiss

I al presently working on a computer port, a port that would give the computer an artificial signal representing the ppo2 of the average of the 2 or 3 senors admitted in the voting logic.

regards

jean mi

cstmwrks · 10th April 2007, 00:51

From this and other posts I have gathered that the LM 324 has lost any standing as far as a worth while op amp for most any rebreather electronics, be it digital or analog. I know for me it has been suspect in a few projects.

What makes the lt1014cn, max 494 or the op490 a better choice? And is the resistor values and basic circuit the same?

rdmmdr · 10th April 2007, 01:07

i use he max they can be had for free, got to love samples. and it is much better at the low end for bleed through.
rick m

**jmurba** · 10th April 2007, 08:40

Quote: (Originally Posted by cstmwrks)

What makes the lt1014cn, max 494 or the op490 a better choice? And is the resistor values and basic circuit the same?

the op490 is has low consuption and works well in single supply, I've always used it...i relly don't know if it is better the yours, compare the datasheets.

regards

jean mi

9th April 2007, 03:50	#1 (permalink)
rdmmdr designer of death Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Mar 2006 Location: kerman,california Posts: 372	analog vrs digital Those of us that feel brave enough or stupid enough to design our own electronics, have pondered the analog vrs digital debate. And after several recent posts i decided it was time to put my two cents in. Analog is a good system if you only want to display o2 levels. while it was used successfully in the Mk/16 series for control. It does not have the adaptive ability that digital control provides. As Kevin, the master of the Mk/16 series, has pointed out. So how does one go about designing their own electronics, or why do we? For the why, it is either an issue of funds or an issue of trust. Some of us cannot afford a new HH, and some of us don't trust the current electronics out there. Why you decide to build your own, is not as important, as what you what them to do. Rebreather electronics fall in to several categories. 1. single cell o2 meters for the dolphin and kiss units for an example 2. triple cell o2 such a Martin's both of these are good examples of analog design that has a long history of service. And a known track record. 3. triple cell digital to a single display 4. triple cell digital to a single display with control 5. and a HUD to any of the above units. for examples one and two, it is not worth the effort to re-engineer the systems it has been done so many times and the equipment is available commercially. But if you want to we will be happy to help. For the digital world, we get in to all kinds of problems. Can you design the hardware?. Can you design the software? What do we what it to do? Do we want to use an adaptive injection algorithm like Kevin? how much data do we want to display at one time? Do we use a 4x20 or an 2x8 display? What are we going to use a an interface? magnets ? tap? How do we do setpoint changes? Do we include deco? So what are the minimum requirements of a digital controller? 1. o2 cells, to provide the data in. 2. op amp to make that data usable for the pic. 3. pic to decide what you are going to do with that data. 4. display 5. output/ solenoid or HUD. design parameters Every systems need to be redundant. We use three cells to insure that, but we tolerate linked controllers ,IE two masters at the same time. The kiss principal needs to be in-place, one controller= one handset and the solenoid. other controller = HUD and handset. i suggest the use of four cells, two for one unit and one channel from the other unit for the third. we can establish 100% isolation from one controller to the other in the cells, and still have three cell voting logic available. The basic principle is that one failure will not effect the next problem. One handset fails,what happens next? This is not included in the current designs. I want a rebreather that will not try to kill me if it has a battery problem, software lock up. That is why i build my own electronics. rick m
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9th April 2007, 17:00	#2 (permalink)
cstmwrks The old ways still work. Current Rebreather/s: Home Build Other Rebreather/s: Not Bought Yet Home Build Join Date: Sep 2006 Location: Boise Idaho Posts: 238	Re: analog vrs digital Quote: (Originally Posted by rdmmdr) Those of us that feel brave enough or stupid enough to design our own electronics, have pondered the analog vrs digital debate. And after several recent posts i decided it was time to put my two cents in. rick m Great input.. I suspect mine was one of those recent posts. When I made my LM 3914 post I never made it real clear my motavation. I'm not on the analog side per say. It is pretty much a fact that digital offers so much more. But that is not my interest. I'm out to come up with a simple analog no frills contoller with voting ability. I do not need deco, I do not need set point adjustment on the fly. I do want an override control.. known as the off switch. Though this is spilling the beans I'm more intersted in building an electrolung clone for no other real reason than to do it. To be as true to the electrolung design as posseble the electronics will be analog. Though I stopped posting about it on any forums the DIY polarographic sensor project has not been forgoten. __________________ Why you ask... well it's not like I have anything better to do.
(Offline)

9th April 2007, 20:42	#3 (permalink)
jmurba wet bear Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: May 2006 Location: cannes france Posts: 920	Re: analog vrs digital Quote: (Originally Posted by rdmmdr) Those of us that feel brave enough or stupid enough to design our own electronics, have pondered the analog vrs digital debate. And after several recent posts i decided it was time to put my two cents in. Analog is a good system if you only want to display o2 levels. while it was used successfully in the Mk/16 series for control. It does not have the adaptive ability that digital control provides. As Kevin, the master of the Mk/16 series, has pointed out. So how does one go about designing their own electronics, or why do we? For the why, it is either an issue of funds or an issue of trust. Some of us cannot afford a new HH, and some of us don't trust the current electronics out there. Why you decide to build your own, is not as important, as what you what them to do. Rebreather electronics fall in to several categories. 1. single cell o2 meters for the dolphin and kiss units for an example 2. triple cell o2 such a Martin's both of these are good examples of analog design that has a long history of service. And a known track record. 3. triple cell digital to a single display 4. triple cell digital to a single display with control 5. and a HUD to any of the above units. for examples one and two, it is not worth the effort to re-engineer the systems it has been done so many times and the equipment is available commercially. But if you want to we will be happy to help. For the digital world, we get in to all kinds of problems. Can you design the hardware?. Can you design the software? What do we what it to do? Do we want to use an adaptive injection algorithm like Kevin? how much data do we want to display at one time? Do we use a 4x20 or an 2x8 display? What are we going to use a an interface? magnets ? tap? How do we do setpoint changes? Do we include deco? So what are the minimum requirements of a digital controller? 1. o2 cells, to provide the data in. 2. op amp to make that data usable for the pic. 3. pic to decide what you are going to do with that data. 4. display 5. output/ solenoid or HUD. design parameters Every systems need to be redundant. We use three cells to insure that, but we tolerate linked controllers ,IE two masters at the same time. The kiss principal needs to be in-place, one controller= one handset and the solenoid. other controller = HUD and handset. i suggest the use of four cells, two for one unit and one channel from the other unit for the third. we can establish 100% isolation from one controller to the other in the cells, and still have three cell voting logic available. The basic principle is that one failure will not effect the next problem. One handset fails,what happens next? This is not included in the current designs. I want a rebreather that will not try to kill me if it has a battery problem, software lock up. That is why i build my own electronics. rick m Hi Rick, as for the reasons to design a digital circuit there are loads of, but the first for me is to be able to built a couple of gauges to be able to always get one to dive. could afford a HH or any other electronics but I could not afford 3 or 4 gauges (((-: I did 5 digital gauges. the second reason is to get exactly what I you need, I need a triple gauges, needed a really audible alarm, I needed a flexible system I could add a hud to without modifying the circuit... I have it. the third reason is the possibility to write and adapt the program... the heart of the system is the program. the fourth is to be sure to be able to repair or built an other circuit in 7 days max... my technical choices were: -Op amp analog devices op490 (quaduple) -Fixed amp op gain (no anlaog calibration) -amplification filtration -Lm 385 2.5v tension ref -16F876 microchip microcotroller, mabye one of the most produced one (there are millions of everywhere), it s well knonw, not new , no surprise, it's programmation is also something really known and mastered. - 2x16 LCD display -5,4 volts supply (6 volts minus the diode) -proton + compiler - no mix between gauge program and deco program (after many hesitations (((- Simplicity was my main strain, classic analog components one can buy throught rs or farnell, hyper classic microcontroller... here is it at the low part of the page : Jean Michel Urbani Kiss I al presently working on a computer port, a port that would give the computer an artificial signal representing the ppo2 of the average of the 2 or 3 senors admitted in the voting logic. regards jean mi __________________ when will I be able to think about something else then spending hours underwater, when will I be normal ? http://web.mac.com/jmurba/Site_2/home.html http://web.mac.com/jmurba/Site_3/home.html
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10th April 2007, 00:51	#4 (permalink)
cstmwrks The old ways still work. Current Rebreather/s: Home Build Other Rebreather/s: Not Bought Yet Home Build Join Date: Sep 2006 Location: Boise Idaho Posts: 238	Re: analog vrs digital From this and other posts I have gathered that the LM 324 has lost any standing as far as a worth while op amp for most any rebreather electronics, be it digital or analog. I know for me it has been suspect in a few projects. What makes the lt1014cn, max 494 or the op490 a better choice? And is the resistor values and basic circuit the same? __________________ Why you ask... well it's not like I have anything better to do.
(Offline)

10th April 2007, 01:07	#5 (permalink)
rdmmdr designer of death Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Mar 2006 Location: kerman,california Posts: 372	Re: analog vrs digital i use he max they can be had for free, got to love samples. and it is much better at the low end for bleed through. rick m
(Offline)

10th April 2007, 08:40	#6 (permalink)
jmurba wet bear Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: May 2006 Location: cannes france Posts: 920	Re: analog vrs digital Quote: (Originally Posted by cstmwrks) What makes the lt1014cn, max 494 or the op490 a better choice? And is the resistor values and basic circuit the same? the op490 is has low consuption and works well in single supply, I've always used it...i relly don't know if it is better the yours, compare the datasheets. regards jean mi __________________ when will I be able to think about something else then spending hours underwater, when will I be normal ? http://web.mac.com/jmurba/Site_2/home.html http://web.mac.com/jmurba/Site_3/home.html
(Offline)

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