For over a year, Scott Shumate has displayed the following doomsday comment regarding the DRO-350 on his web site (Shumatech.com).
"WARNING!!! The DRO-350 is an old design that uses obsolete parts. The DRO-350 has a number of problems including scale jitter, rounding errors, and axes that won't display. These problems will not be fixed and all future development activity will concentrate on the DPU-550 and DRO-550. The DRO-550 completely solves all of these problems and adds a huge list of new features."
"WARNING!!! The DRO-350 is an old design that uses obsolete parts. The DRO-350 has a number of problems including scale jitter, rounding errors, and axes that won't display. These problems will not be fixed and all future development activity will concentrate on the DPU-550 and DRO-550. The DRO-550 completely solves all of these problems and adds a huge list of new features."
With over 6 years to solve these problems (2003-2009) one might wonder why, with basically the same circuitry, the DRO-550 is providing a miraculous solution to this problems.
At Wildhorse Innovations we have had many inquiries regarding the dire warnings and extreme statements contained in that post. This blog post is an attempt to bring to light the true status and nature of the the DRO-350. Whenever opinions are expressed in this post, they will be clearly labeled as such. However, even the opinions are not lacking in facts. They are based upon over 40 years of experience in the field of electronics and an earnest effort has been made to exclude personal prejudices from the opinions stated.
"The DRO-350 is an old design": True. The DRO-350 was originally designed around 2003 and not much has changed in the meantime. It was, and is, a stable well designed DRO for use with what are commonly referred to as "Chinese" scales. The DRO-350 is so well designed that the most critical portions of the design are DIRECTLY imported into the DRO-550 (the scale interfaces and the AUX/TACH interfaces). A side by side comparison of the schematics of the DRO-350 and the DRO-550 will show that the primary differences occur in the power supply section (providing 3.3vdc for the MPU) and the various additional interfaces added. It might be noted that many of the "New" interfaces are non-functional because no software has been developed for them.
"WARNING!!! The DRO-350 is an old design that uses obsolete parts.": Partly True. To paraphrase the infamous words of President Bill Clinton, "It depends on the meaning of obselete.". Have you ever gone to an auto parts store with a part number only to discover that the part has been superseded by a new part? Is your old part "number" obselete? Yes. Is there a new part that bolts in place, performs the same function and allows you car to function in exactly the same manner as with the "old" part? Yes.
So it is with electronics. Manufacturers will change part numbers for a number of reasons. Over the past dozen or so years, EPA regulations and the ECM's ROHS standards have forced manufacturers to redesign parts to eliminate what have been deemed hazardous substances. Some manufacturers have merely made minor changes to parts to meet the new regulations and stuck an additional prefix or suffix on the part number. Others have taken the opportunity to increase the overall functionality of the part and relabeled the part with a totally new part number.
So what is the bottom line for the DRO-350. ALL PARTS FOR THE DRO-350 ARE CURRENTLY IN PRODUCTION. Have part numbers changed? Yes. But we at Wildhorse Innovations continue to provide our customers with all necessary cross-references so you can readily identify any parts on which the identifying numbers have changed.
"The DRO-350 has a number of problems including scale jitter": This issue has been a thorn in the side of "Chinese" scales since day one. Little, if any of the problem can be solved in the design of the DRO-350 (or the DRO-550) or the software. The problem lies in several areas.
First, the "Chinese" scales are not really designed to be used with a remote head (the DRO-350 or DRO-550). They are not designed to use an external power supply. They are designed to receive their power from the 1.5vdc "button" batteries that are inserted into them.
Second, the "Chinese" scales determine "position" by measuring the varying capacitance that is present between the scale readout and the rail as the readout moves along the scale.
These conditions make up the bulk of the jitter issue.
When we provide the power for the scale from an "outside" source (such as the DRO-350), we are sending this power through a rather lengthy cable which is subject to all manner of EMF influences. Couple that with the fact that the power transmitted through the cable is VERY low (1.5vdc at a few milliamps) and you have a perfect formula for disturbing influences from outside EMF. As mentioned above, the circuitry in the scale readout is "expecting" to receive rather stable power from a battery mounted just a fraction of an inch away. The circuitry is not designed to cope with the possibility of fluctuating supply voltages.
Another influence on the jitter issue is that the "Chinese" scales determine position by measuring the capacitance between the readout (sliding portion of the scale) and the scale rail. Obviously anything that influences that capacitance will alter the scale reading and introduce jitter. These influences can include improper grounding of the scales (or creating ground loops), introducing vibration into the scale as the machine is running or ANY source of EMF acting upon the scale itself or the cables connecting the scale to the DRO head.
There have been many "solutions" to the jitter issue. (Any belief that the jitter issue was solved with the DRO-550 is quickly disspelled by a quick perusal of the ShumaTech forum.) Some have involved leaving the battery in the scale. Some involve installing capacitors in the battery compartment of the scale. At Wildhorse Innovations we have found the following steps solve 99% of the jitter problem.
1. Keep cable runs as short as possible.
2. Route the cables inside the DRO-350 case in areas away from the display section of the PCB.
3. If using shielded cable, ground the shield ONLY at the scale end of the cable.
4. Route cables so as to avoid EMF interference. NEVER run scale cables parallel to high voltage cables. Also, NEVER run scale cables parallel to stepper motor cables.
5. Most scale head bodies are connected to the negative side of the power supply. When mounting the scales, insulate the bodies from the machine. Failure to properly insulate the scale head bodies can result in ground loops.
6. Mount the scales to the machine so as to minimize the transmission of vibration from the machine to the scale.
"rounding errors": True. You carry your calculations past 5-6 decimal points, the DRO-350 has rounding problems. So you guys that are working with tolerances in the 0.00001" range probably need a different DRO.
"axes that won't display": To be honest, we at Wildhorse Innovations have never seen this problem in a standard DRO-350. We have seen it in DRO-350 with DPU-550 daughter boards, but it is rare and since the DPU-550 is no longer produced, it appears to be a non-issue for the new purchaser.
"These problems will not be fixed": Easy solution Scott. Release the source of for the DRO-350 as Open-Source. Let the market place find the solutions. There is a new drop in replacement for the PIC16F MPU used in the DRO-350 (the PIC18F) that has over 3-1/2 times the memory of the PIC16F and an improved, more powerful instruction set. It costs only about $1.00 more than the PIC16F, so any increase in cost of the DRO-350 would be minimal. Additionally, since it is a literal drop in replacement, every DRO-350 in existance could be upgraded for under $15.00.
"The DRO-550 completely solves all of these problems": Sorry, but to be blunt, this is a total falsehood. I'm not saying the DRO-550 does not have it's up side, but 10 minutes on the ShumaTech forum will show that the DRO-550 has its share of problems and solutions are sometimes slow in coming. Scott has a stranglehold on the software and it almost seems that if it is not Scott's idea, it doesn't make it into the code. And after over 2 years, we have yet to reach release 1.0.
"and adds a huge list of new features.": Absolutely true! And if they are features you need/want and are willing to pay for, then there is no reason to not purchase a DRO-550 (when you can find one). The ability to mix and match different protocols is a hugh advantage for those that need it. (Did we mention that this same feature could be an upgrade to the DRO-350 if Scott were to release the source code?) And the advertized features that don't yet work will be a real plus when they go live. I'm sure target dates will be announced soon.
At Wildhorse Innovations we have had many inquiries regarding the dire warnings and extreme statements contained in that post. This blog post is an attempt to bring to light the true status and nature of the the DRO-350. Whenever opinions are expressed in this post, they will be clearly labeled as such. However, even the opinions are not lacking in facts. They are based upon over 40 years of experience in the field of electronics and an earnest effort has been made to exclude personal prejudices from the opinions stated.
"The DRO-350 is an old design": True. The DRO-350 was originally designed around 2003 and not much has changed in the meantime. It was, and is, a stable well designed DRO for use with what are commonly referred to as "Chinese" scales. The DRO-350 is so well designed that the most critical portions of the design are DIRECTLY imported into the DRO-550 (the scale interfaces and the AUX/TACH interfaces). A side by side comparison of the schematics of the DRO-350 and the DRO-550 will show that the primary differences occur in the power supply section (providing 3.3vdc for the MPU) and the various additional interfaces added. It might be noted that many of the "New" interfaces are non-functional because no software has been developed for them.
"WARNING!!! The DRO-350 is an old design that uses obsolete parts.": Partly True. To paraphrase the infamous words of President Bill Clinton, "It depends on the meaning of obselete.". Have you ever gone to an auto parts store with a part number only to discover that the part has been superseded by a new part? Is your old part "number" obselete? Yes. Is there a new part that bolts in place, performs the same function and allows you car to function in exactly the same manner as with the "old" part? Yes.
So it is with electronics. Manufacturers will change part numbers for a number of reasons. Over the past dozen or so years, EPA regulations and the ECM's ROHS standards have forced manufacturers to redesign parts to eliminate what have been deemed hazardous substances. Some manufacturers have merely made minor changes to parts to meet the new regulations and stuck an additional prefix or suffix on the part number. Others have taken the opportunity to increase the overall functionality of the part and relabeled the part with a totally new part number.
So what is the bottom line for the DRO-350. ALL PARTS FOR THE DRO-350 ARE CURRENTLY IN PRODUCTION. Have part numbers changed? Yes. But we at Wildhorse Innovations continue to provide our customers with all necessary cross-references so you can readily identify any parts on which the identifying numbers have changed.
"The DRO-350 has a number of problems including scale jitter": This issue has been a thorn in the side of "Chinese" scales since day one. Little, if any of the problem can be solved in the design of the DRO-350 (or the DRO-550) or the software. The problem lies in several areas.
First, the "Chinese" scales are not really designed to be used with a remote head (the DRO-350 or DRO-550). They are not designed to use an external power supply. They are designed to receive their power from the 1.5vdc "button" batteries that are inserted into them.
Second, the "Chinese" scales determine "position" by measuring the varying capacitance that is present between the scale readout and the rail as the readout moves along the scale.
These conditions make up the bulk of the jitter issue.
When we provide the power for the scale from an "outside" source (such as the DRO-350), we are sending this power through a rather lengthy cable which is subject to all manner of EMF influences. Couple that with the fact that the power transmitted through the cable is VERY low (1.5vdc at a few milliamps) and you have a perfect formula for disturbing influences from outside EMF. As mentioned above, the circuitry in the scale readout is "expecting" to receive rather stable power from a battery mounted just a fraction of an inch away. The circuitry is not designed to cope with the possibility of fluctuating supply voltages.
Another influence on the jitter issue is that the "Chinese" scales determine position by measuring the capacitance between the readout (sliding portion of the scale) and the scale rail. Obviously anything that influences that capacitance will alter the scale reading and introduce jitter. These influences can include improper grounding of the scales (or creating ground loops), introducing vibration into the scale as the machine is running or ANY source of EMF acting upon the scale itself or the cables connecting the scale to the DRO head.
There have been many "solutions" to the jitter issue. (Any belief that the jitter issue was solved with the DRO-550 is quickly disspelled by a quick perusal of the ShumaTech forum.) Some have involved leaving the battery in the scale. Some involve installing capacitors in the battery compartment of the scale. At Wildhorse Innovations we have found the following steps solve 99% of the jitter problem.
1. Keep cable runs as short as possible.
2. Route the cables inside the DRO-350 case in areas away from the display section of the PCB.
3. If using shielded cable, ground the shield ONLY at the scale end of the cable.
4. Route cables so as to avoid EMF interference. NEVER run scale cables parallel to high voltage cables. Also, NEVER run scale cables parallel to stepper motor cables.
5. Most scale head bodies are connected to the negative side of the power supply. When mounting the scales, insulate the bodies from the machine. Failure to properly insulate the scale head bodies can result in ground loops.
6. Mount the scales to the machine so as to minimize the transmission of vibration from the machine to the scale.
"rounding errors": True. You carry your calculations past 5-6 decimal points, the DRO-350 has rounding problems. So you guys that are working with tolerances in the 0.00001" range probably need a different DRO.
"axes that won't display": To be honest, we at Wildhorse Innovations have never seen this problem in a standard DRO-350. We have seen it in DRO-350 with DPU-550 daughter boards, but it is rare and since the DPU-550 is no longer produced, it appears to be a non-issue for the new purchaser.
"These problems will not be fixed": Easy solution Scott. Release the source of for the DRO-350 as Open-Source. Let the market place find the solutions. There is a new drop in replacement for the PIC16F MPU used in the DRO-350 (the PIC18F) that has over 3-1/2 times the memory of the PIC16F and an improved, more powerful instruction set. It costs only about $1.00 more than the PIC16F, so any increase in cost of the DRO-350 would be minimal. Additionally, since it is a literal drop in replacement, every DRO-350 in existance could be upgraded for under $15.00.
"The DRO-550 completely solves all of these problems": Sorry, but to be blunt, this is a total falsehood. I'm not saying the DRO-550 does not have it's up side, but 10 minutes on the ShumaTech forum will show that the DRO-550 has its share of problems and solutions are sometimes slow in coming. Scott has a stranglehold on the software and it almost seems that if it is not Scott's idea, it doesn't make it into the code. And after over 2 years, we have yet to reach release 1.0.
"and adds a huge list of new features.": Absolutely true! And if they are features you need/want and are willing to pay for, then there is no reason to not purchase a DRO-550 (when you can find one). The ability to mix and match different protocols is a hugh advantage for those that need it. (Did we mention that this same feature could be an upgrade to the DRO-350 if Scott were to release the source code?) And the advertized features that don't yet work will be a real plus when they go live. I'm sure target dates will be announced soon.
Now for an opinion. The DRO-550 is a throw away board. By this I mean, when something goes wrong, (borrowing from "Ghost Busters") "Who ya gonna call?". The DRO-550 is a 4 layer, surface mount board. If you look at the repair services, only the most expensive multilayer SMT boards are repaired. It's time consuming, requires special equipment and expensive to repair these types of boards. Plus, with the small number of DRO-550 boards produced, no repair house can afford to set up the "line" and train personnel to repair the small number of repairs that would come in. But when it's your board that needs repair, one is not a "small" number.
We get emails virtually every week asking about repairs for the DRO-550. The only advise we can give is "buy a new board".
This is not Scott's fault. But he could set up an exchange program to ease the pain for the customer. Yes, he will most likely junk the old board, but at least he has acknowledged the value of the customer for having purchased the DRO-550 in the first place.
BOTTOM LINE:
The DRO-350 is alive and well. It's a workable, inexpensive solution for the home machinist on a budget. Wildhorse Innovations is dedicated to supporting it for as long as possible, which we expect to be years into the future.
When used with the "Chinese" scales, it's a bargain. When used with quadrature scales, including the Igaging scales, the DRO-550 is probably a better buy, until and unless, Scott will release the source code for the DRO-350. We can then produce a low cost upgrade. It won't be a DRO-550, but it will meet the needs of many customers.
As usual your comments are welcome. Visit us at http://www.wildhorse-innovations.com.
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