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### Question #: 274

Question: FIRST OF ALL, THANKS FOR DESIGNING A WONDERFUL SITE. MY QUESTION IS: HOW DO YOU CALCULATE EME (ELECTROMAGNETIC EMISSIONS) AROUND THE TRANSMITTER (ANTENNA) AT ANY GIVEN POINT AND WHAT ARE MEASURES TO KEEP IT UNDER SAFETY CODE?

Current Solution

Conceptually it is straightforward to predict the radiofrequency (RF) exposure intensity at any point in the vicinity of a cellular radio base station antenna. Simply multiply the effective radiation power times the inverse square of the distance times the relative gain of the antenna in the direction of the interest. The relative gain in different directions is know as the antenna radiation pattern and is usually available from the antenna manufacturer in graphical or tabular form.

Unfortunately, in real life the calculations involved in base station antenna evaluations are quite complex and require expert knowledge and experience to deal with the many parameters that are involved. An excellent reference summarizing this process is the Federal Communications Commission OET Bulletin No. 65 titled "Evaluating Compliance With FCC Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields," available on the Federal Communications Commission (FCC) website.

To assess the RF hazards associated with handheld cell phones it is necessary to predict the rate of absorption in the body of radiofrequency energy, a parameter called the specific absorption rate (SAR). This is a very complex calculation, and cell phone manufacturers often rely on measurements of SAR in fluid-filled cylinders or plastic containers in the shape of a head. The FCC requires cell phone manufacturers to provide this data to FCC. You can obtain the data for your model phone on the the FCC's website. Unfortunately only cell phones manufactured in the last couple years are listed here.

As to your question about keeping RF exposures within the safety code, please read the other questions posted on this website this matter. Cellular radio products that meet FCC requirements will be within the guidelines established by safety standards organizations for users' and public exposure to RF radiation fields.

Gary H. Zeman, ScD, CHP

Respond:

### Other Possible Solutions to this Question

• hello there, i am using servo motor for my X and Y Axis but i dont know how to calculate steps/mm for that, the lead screw i am using is have pitch of .5 mm. please helpme on this i have done everything only this point is pending.

The formula for finding the steps per mm is found in the units itself. First, you mentioned that the motor is a servo. This needs to be clarified as a servo is different than a stepper motor. Some servos behave similar to a stepper motor, so I will continue with this in mind.

The formula is (steps/mm):

You need to find the steps. The stepper motor has a natural number of steps per a full revolution. This is typically 200 steps per revolution.

The driver for the stepper motor allows you to increase the number of steps per revolution by adding a specified number of steps between each step. For instance, if you set the driver to 1/4 microstepping, then instead of having 200 steps per revolution, you would have 200 x 4 = 800 steps per revolution.

So now we have the first part of the formula:

Steps / mm = (200 x 4) / mm

Lets determine the mm side of the formula:

You mention that the pitch is 0.5 mm. Check to insure that the lead is also 0.5 mm. This could be a multiple start lead screw where the pitch is different than the turns per mm. If in this case, that the 0.5 mm is the travel for one full revolution, then you can simply plug this into the formula as:

mm = .5 mm

Otherwise, determine how fat the travel is for one complete revolution.

Therefor, with what we know and the driver is set at 1/4 microstepping and the stepper motor has a natural step count per revolution at 200:

steps / mm = (200 steps x 4) / 0.5 mm = 800 steps / 0.5 mm = 1600 steps / mm

If your travel for one revolution is not 0.5 mm, then plug in your travel distance instead.

i know about steps/mm calculation for stepper motor, because i am using servo motor that why i asked about that. please tell for servo motor.

because its my first time with servo motor i have no idea about calculation of parameter with servo.

Have you attempted to contact the manufacturer or seller of the servo? We typically respond to customers of our products on this customer service area, unless we have extensive knowledge of the subject and can answer the question efficiently.

• I have wired up my 110v VFD and my 2.2Kw spindle and I get an E.Lu.5 code. My wiring is correct and the parameters are set to those for the VFD according to your website I found in a previously answered question from someone here. Any help would be greatly appreciated, thank you!!

The E.Lu.5 Error code on your VFD is related to Low Voltage.

The recommended action is:
- 1. Check whether the input voltage is normal. (the voltage from the wall/breaker to the VFD)
- 2. Check whether there is a sudden change in load.
- 3. Check whether there is any phase missing.

Unfortunately, these three recommended actions will probable require an electrician to test the line going into the VFD.

• Hello I recently read your site and have a question. I have a driver model DM2722A but I can't connect it to my usb controller due to the fact that the driver is not marked enable, but instead it is marked: mf-, mf +, alm-, alm +. I will be very grateful if you explain to me the meaning of the latter and tell me what should be related to "enable" Thanks in advance!

Not a problem. The ALM is rather self-explanatory as this is a closed-loop stepper motor and driver that you are using. The ALM (alarm) is a signal that is used to tell the driver/controller that the motor is not in the same condition that the driver expects. In a closed-loop system, the motor has an encoder that tells the driver exactly how many steps that it turned, and if this value does not coincide with the driver's outputted number of steps, and within a specified amount of time, the alarm will trigger so the system can stop and the workpiece can be salvaged.

The MF is simply a signal that tells the driver that there is impending direction and step pulses coming. If the MF signal is high, then that is similar to an enable signal.

• I WIRED MY VFD (2.2KW VERSION) AND TRIED TEST RUNNING THE SPINDLE. CONFIGURED TO YOUR SPECS ON THIS WEBSITE, ONLY ISSUE IS WE GOT AN ERROR CODE. ERR 02, DO YOU KNOW WHAT IS? OR HAVE A LIST OF CODES? THANK

Can you provide the model number of your VFD?

Yes, I have the "YL600 - 2S - 2K20"

It just came with a small booklet that is all in Chinese...

I WIRED MY VFD (2.2KW VERSION) AND TRIED TEST RUNNING THE SPINDLE. CONFIGURED TO YOUR SPECS ON THIS WEBSITE, ONLY ISSUE IS WE GOT AN ERROR CODE. ERR 02, DO YOU KNOW WHAT IS? OR HAVE A LIST OF CODES? THANK

• For the 1/2'' 5 start ACME leadscrew, what is the length purchased for the \$2.00 order? and if you make 2 orders, are you getting two separate rods or 1 rod at twice the length. Thanks.

We sell our ACME screws in total length (overall length you require), but if individual lengths are needed you can contact us via phone (281-815-7701) or email (customerservice@buildyourcnc.com).

A \$2.00 order will be a total of 1 inch, but if ordered separately then you will receive 2 of the same length.

For the 1/2'' 5 start ACME leadscrew, what is the length purchased for the \$2.00 order? and if you make 2 orders, are you getting two separate rods or 1 rod at twice the length. Thanks.

• THERE HAS BEEN A CELL PHONE BASE INSTALLED IN THE FIRE TOWER. PANELS ARE VERTICAL AND LOCATED ABOUT 75 FEET AT TOP OF UNLIKE SOME TOWERS I HAVE SEEN NO ROUND DISKS BEAMING LIGHTS. NIGHT, TOWER MATERIAL DARK. DOES THIS MAKE ANY DIFFERENCE RELATED HEALTH ISSUES WITH RF EXPOSURE IT POSSIBLE RECEIVE-ONLY TRANSMITTER ?

There has been a cell phone base installed in the fire tower. The panels are vertical and located about 75 feet at the top of the tower. Unlike some towers I have seen there are no round disks and no beaming lights. At night, the tower and cell phone material are dark. Does this make any difference in any related health issues with RF exposure and is it possible the tower is a receive-only transmitter ?

• Hey ! I have purchased a VFD with matching spindle 1.5kW and control program UCCNC. And my interface card is DB25, the question is how do I connect the VFD to DB25 so that I can control the speed with UCCNC? Sincerely "cnc beginners"

Identify the Control Signals: First, determine which control signals from the DB25 interface card are used for spindle speed control. Typically, these are PWM (Pulse Width Modulation) signals or analog voltage signals.

VFD Configuration: Your VFD should be configured to accept the type of control signal your DB25 card provides. This involves setting parameters in the VFD that correspond to the type of input signal it will receive for speed control.

Wiring: Connect the appropriate output pins from the DB25 card to the input terminals on the VFD. This usually involves connecting the PWM or analog output to the corresponding input on the VFD. Make sure to consult the manuals for both your VFD and interface card for specific wiring details.

UCCNC Settings: Configure UCCNC to output the correct type of signal (PWM or analog) that matches your VFD's configuration. This is done through the software's spindle setup section.

Test and Adjust: Run some tests to ensure that the spindle speed is being correctly controlled by UCCNC. You might need to tweak settings in either the VFD or UCCNC for optimal performance.

• I build custom speakers and I work primarily with 5'x5' sheets of 9 ply (1/2") and 13 ply (3/4") plywood, but I occassionally cut 2" nominal thick wood as well. What kit would you recommend? Are your systems accurate enough to do angle cuts (45 deg?) thanks

The best machine due to the width, will be the greenBull 5x which would have a cutting surface of 5' x 10'. Also our machines with spindle are accurate for 1000's of an inch, and can do 45 degree angle cuts.

• Regarding 1/2" 5 start and 10 TPI ACME precision lead screw, what the maximum length you can ship within USA? I'm looking for something like 100" and I could use a 1" screw if available. Please include estimated price. Thanks.

The maximum length we can ship is a total of 78" inches. However we can send your required length in portions. Please refer to adding the total items you require to your cart to get a visualized amount and shipping cost.

• If I wired my stepper motors incorrectly what parts of the electronics will be ruined? When I turn on the power, my motors jump like they are supposed to but for some reason, the G-code doesn't seem to be moving from Mach 3 to the motors. Any help would be appreciated. Do I need to order new electronics or just part of the system? Thanks

The drivers have quite a bit of protection, so you probably won't ruin anything. You motors are jumping and that is just the motors engaging from getting power from the power supply.

There could be many reasons your motors don't turn. Consider these troubleshooting tips:

- If you are using our parallel breakout board, make sure that the step pins are set for active low (config -> Ports and Pins -> Motor Outputs -> the steps pins should be enabled and set active low)

- The parallel breakout board is powered (connect the USB to the computer using a USB cable)

- In Mach3, make sure you have jog enabled (a little green button at thelower middle of the page in the program run screen).

DS26

• I would like to design my own CNC router around one of your electronics bundles, either the 3 Axis - Heavy Gantry or 3 Axis - All Large Motors. Do you have the data sheets for the motors so that I can use the dimensions in my model?

You can find the datasheets to our motors be going to the the stepping motor category page https://www.buildyourcnc.com/category/nema and selecting the motor. This will bring you to the product page for the motor and all of the motor information will be found there.

• HEY ! I HAVE PURCHASED A VFD WITH MATCHING SPINDLE 1.5KW AND CONTROL PROGRAM UCCNC. MY INTERFACE CARD IS DB25, THE QUESTION HOW DO CONNECT TO DB25 SO THAT CAN SPEED UCCNC? SINCERELY "CNC BEGINNERS"

Identify the Control Signals: First, determine which control signals from the DB25 interface card are used for spindle speed control. Typically, these are PWM (Pulse Width Modulation) signals or analog voltage signals.

VFD Configuration: Your VFD should be configured to accept the type of control signal your DB25 card provides. This involves setting parameters in the VFD that correspond to the type of input signal it will receive for speed control.

Wiring: Connect the appropriate output pins from the DB25 card to the input terminals on the VFD. This usually involves connecting the PWM or analog output to the corresponding input on the VFD. Make sure to consult the manuals for both your VFD and interface card for specific wiring details.

UCCNC Settings: Configure UCCNC to output the correct type of signal (PWM or analog) that matches your VFD's configuration. This is done through the software's spindle setup section.

Test and Adjust: Run some tests to ensure that the spindle speed is being correctly controlled by UCCNC. You might need to tweak settings in either the VFD or UCCNC for optimal performance.

HEY ! I HAVE PURCHASED A VFD WITH MATCHING SPINDLE 1.5KW AND CONTROL PROGRAM UCCNC. MY INTERFACE CARD IS DB25, THE QUESTION HOW DO CONNECT TO DB25 SO THAT CAN SPEED UCCNC? SINCERELY "CNC BEGINNERS"

• BUILDING ONE OF YOUR GREENBULL 6X LONG AND 2.2 KILOWATT SPINDLE DOES NOT FIT. SEEMS LEAD SCREW YOU SENT WITH KIT IS SHORT 42" LOOKS LIKE IT NEEDS TO BE 5 OR 6 INCH LONGER. THIS CORRECT? WHAT THE NEEDED LENGTH FOR UNIT?

The leadscrew length for the greenBull long Z-axis is 47 inches.

• In the Build your own CNC machine book, You said you use 1 1/4" angle on the main table but 1" would be better. So my question is Should I use 1" angle on the main table (4' length) and 1 1/4" angle for the BRA's and other rails?

You can use either 1" x 1" x 1/8", or 1-1/4" x 1-1/4" x 1/8" angle on the table sides. The BRAs should all be 3/4" x 3/4" x 1/8". The Y ans Z axes should use the 3/4" x 3/4" x 1/8" angles.

• Hi, on adding an item to cart and entering shipping information, the first class mail charges are fine, but the courier service charges are being shown to be outrageously expensive, in the range of 249 dollars for India. Are you sure this isnt some technical glitch?

Depending on the actual items added to the cart, the price for shipping internationally will be high (ex. Our CNC machines/Computer CNC Systems) or low (ex. breakout board/s, cable, end mills, etc.) on certain items. However dealing with USPS first class mail it should be in the low cost shipping options, please try again at a later time and please check shipping address for any errors.

If issue proceeds please email us at customerservice@buildyourcnc.com for further assistance.

• Could you please e-mail us the invoice for the order, shipment is currently at the customs and your invoice is needed so it can be cleared. As I can't seem to find any order number or other reference in your system, the only reference I have is the tracking number LZ676176940US and the order date is 12/26/2017. Thanks!

I just sent you the commercial invoice via email. Thanks.

• Regarding L6203/L297 Stepper Board Driver, would you be willing to sell two unpopulated boards? A friend and I are each building a low cost CNC and I already have most of the components. Thanks.

We don't hold those boards in-house anymore. You can use the schematic to form your own boards if you wish.

Thanks for the reply. Has this proven to be a good design?

Regarding L6203/L297 Stepper Board Driver, would you be willing to sell two unpopulated boards? A friend and I are each building a low cost CNC and I already have most of the components. Thanks.

• Hello. I like your vertikal router. Is then router stabil enogh for the need of a Carpenter? Are you using 21mm Plywood or 21mm MDF. What type of spindel (KW) is maximum allowed and whatbis the maximum feed (6mm cutter) in oak. Thank you, Veit

The greenLean vertical CNC is stable enough to handle large-scale production on a daily basis. We use 3/4" MDO plywood, which is equivalent to about 19mm. The gantry is designed to hold a 2.2kW Spindle, with a maximum of 24,000 RPM.

• Placed an order for the cable set for the Pokeys57cnc interface on 10/20 but it is not showing up in My Account as being ordered. It was charged to my credit card and I have not had any info that it was received by you.

Sure, let me check.

Your order was shipped out on Tuesday (10/20/2020). I noticed that your email was not stored in the customer record when the order was made. I will send you the tracking number via email now.

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