Posts Tagged ‘power supply’

DIY Powerpole voltage and current meters

Powerpole voltage and current monitoring is quite nice to have. One can buy commercial meters, but due to the availability of nice and cheap modules, it is very easy to make them oneself.

To the right you’ll see my combined voltage and current meter as well as my volt-meter on top of the power supply.

Both of the modules have been bought on Ebay:

  • Miniature 0-30 V DC LED 2 wire Digital voltmeter (371333527599) where the display is 22 by 10 mm. Cost slightly more than $1
  • 0-100 V, 0-10 A Dual Voltmeter Ammeter (262455987311) costing less than $3. The module size is 48 x 29 x 26 mm and the letters are 7 mm tall just like the miniature voltage display.
The wires to the voltmeter are connected directly to PowerPole connectors as shown in the second figure (upper right). Then the voltmeter itself is enclosed in transparent shring-wrap tubing of diameter approximately 20 mm like the one you also can buy on Ebay (252004328030).
The voltage-current meter is a little more complex to connect. First the volt meter has a power lead (4-30 V) and a measurement lead (0-100 V) which are connected together as I will only be using it for 12 Volts. The current measurement loop is between the negative, black, PowerPole connectors. The positive, red, PowerPole connectors are wired together.
I hope this can inspire others to make something similar. And if you do, then please let me know in the comments field!

The post “DIY Powerpole voltage and current meters” first appeared on the LA3ZA Radio & Electronics page.

DIY Powerpole voltage and current meters

Powerpole voltage and current monitoring is quite nice to have. One can buy commercial meters, but due to the availability of nice and cheap modules, it is very easy to make them oneself.

To the right you’ll see my combined voltage and current meter as well as my volt-meter on top of the power supply.

Both of the modules have been bought on Ebay:

  • Miniature 0-30 V DC LED 2 wire Digital voltmeter (371333527599) where the display is 22 by 10 mm. Cost slightly more than $1
  • 0-100 V, 0-10 A Dual Voltmeter Ammeter (262455987311) costing less than $3. The module size is 48 x 29 x 26 mm and the letters are 7 mm tall just like the miniature voltage display.
The wires to the voltmeter are connected directly to Powerpole connectors as shown in the second figure (upper right). Then the voltmeter itself is enclosed in transparent shring-wrap tubing of diameter approximately 20 mm like the one you also can buy on Ebay (252004328030).
The voltage-current meter is a little more complex to connect. First the volt meter has a power lead (4-30 V) and a measurement lead (0-100 V) which are connected together as I will only be using it for 12 Volts. The current measurement loop is between the negative, black, Powerpole connectors. The positive, red, Powerpole connectors are wired together.
I hope this can inspire others to make something similar. And if you do, then please let me know in the comments field!

The post “DIY Powerpole voltage and current meters” first appeared on the LA3ZA Radio & Electronics page.

Series capacitors that failed according to the book

0.33 uF X2 capacitors which measured only
0.097, 0.1, and 0.118 uF.

Many devices now use a capacitor power supply saving the space that a mains transformer occupies. The principle is that a series capacitor from the mains supply is used to drop the voltage and reduce the current. Provided that the circuit is completely isolated from human touch, this is an economical way to provide DC power.

The image shows three such capacitors as I were measuring them. They came from three malfunctioning devices in my home: two wall-mounted thermostats for floor heating and a remote controlled mains switch.

Their power supplies were designed with a capacitor of 330 nF in series with a bridge rectifier which supplies the low voltage DC. This value is typical, it seems for 230 Vac, 50 Hz circuits that are designed for about 20 mA. The value will be higher for an equivalent 115 Vac, 60 Hz circuit.

The malfunctioning happened because the value of the capacitor in my cases was reduced to 1/3 and less of the nominal value. These capacitors are all marked X2 and a voltage of 275 Vac.

The X2 means that they are safety capacitors which will not fail by short-circuiting as this would be a fire hazard in this circuit. They have self-healing properties and that means that they fail by “burning away” on their own foil, leading to a reduction in capacitance and eventually failure of the circuit as the power supply cannot supply the required current any more. They should never be replaced by anything but X2 capacitors with the same or higher voltage rating.

Go to the Wikipedia page Capacitive power supply for more description of this circuit.

By the way, the devices which these capacitor came from were 15 year old Microtemp MTN-1991 thermostats and a 20 years old Nobø System 500 RCE512 remote receiver.

Series capacitors that failed according to the book

0.33 uF X2 capacitors which measured only
0.097, 0.1, and 0.118 uF.

Many devices now use a capacitor power supply thus saving the space that a mains transformer occupies. The principle is that a series capacitor from the mains supply is used to drop the voltage and reduce the current. Provided that the circuit is completely isolated from human touch, this is an economical way to provide DC power.

The image shows three such capacitors as I were measuring them. They came from three malfunctioning devices in my home: two wall-mounted thermostats for floor heating and a remote controlled mains switch.

Their power supplies were designed with a capacitor of 330 nF in series with a bridge rectifier which supplies the low voltage DC. This value is typical, it seems, for 230 Vac, 50 Hz circuits that are designed for about 20 mA. The value will be higher for an equivalent 115 Vac, 60 Hz circuit.

The malfunctioning happened because the value of the capacitor in my cases was reduced to 1/3 and less of the nominal value. These capacitors are all marked X2 and a voltage of 275 Vac.

The X2 means that they are safety capacitors which will not fail by short-circuiting as this would be a fire hazard in this circuit. They have self-healing properties and that means that they fail by “burning away” on their own foil, leading to a reduction in capacitance and eventually failure of the circuit as the power supply cannot supply the required current any more. They should never be replaced by anything but X2 capacitors with the same or higher voltage rating.

Go to the Wikipedia page Capacitive power supply for more description of this circuit.

By the way, the devices which these capacitor came from were 15 year old Microtemp MTN-1991 thermostats and a 20 years old Nobø System 500 RCE 512 remote receiver. They now all work again thanks to the fitting of new 0.33 uF capacitors. And all of them are safety capacitors of type X2 of course – no gambling with safety here.

Troubles with the FT-950

Having some issues with my Yaesu FT-950. On Friday I noticed the 950 had a high SWR reading on 40m. Tried tuning and it wouldn’t correct the issue. I went back to 20m and over the weekend worked almost 200 SSB contacts without issue and was receiving solid signal reports on my audio all weekend long. Last night I tried working W1AW/5 on 40m and again couldn’t get the 950 to tune.

I decided to connect the 950 to a dummy load and check it out. I used my LDG AT-600ProII and the analog meter in bypass mode to record the following measurements with the FT-950 in CW mode and sending a continuous carrier.

10m – flat SWR and 50w fwd power
12m – flat SWR and 35w fwd power
15m – flat SWR and 25w fwd power
17m – flat SWR and 15w fwd power
20m – flat SWR and 10w fwd power
30m – flat SWR and 0w fwd power
40m – flat SWR and 0w fwd power
80m – flat SWR and 0w fwd power
160m – flat SWR and 0w fwd power

About 15 minutes later I repeated the tests, which produced different results as noted below:

10m – 35w
12m – 20w
15m – 15w
17m – 10w
20m – 5w
30m – 0
40 – 0
80 – 0
160 – 0

I’m a bit perplexed as to what is going on. I’m going to try another power supply tonight, but I have a feeling the 950 will need to take a trip to California and spend some time in the Yaesu hospital. I’ve also performed a full factory reset, but still getting the same results. Anyone else have any other bright ideas?

If the 950 does need to take a trip to California, I’m hoping Yaesu can turn it around in time to have it back for my stint operating W1AW/Ø.

Until next time…

73 de KDØBIK

Show Notes #092

Introduction:

Announcements:

  • Texoma Hamarama will held October 26-27, 2012 at the Ardmore Convention Center in Ardmore, Oklahoma. Pre-registration ends October 20th.
  • The Augusta Hamfest will be Saturday, October 13, 2012 in Augusta, GA.
  • Scott, N8VSI, was the LHS ambassador at the Ohio LinuxFest, September 28-30, 2012. We look forward to hearing a report from Scott in the near future.

Topics:

  • Richard recounts his experience replacing a computer power supply. Moral? Don’t be afraid to try repairing a computer yourself. Swapping parts is easier than you might think. For power supplies, pay attention to the wattage required. (Ed. Note: When in doubt, it’s best to replace the bad supply with one that has the same or greater wattage rating.)
  • Departing from our usual topics, Russ and Richard discuss a couple applications for producing slide shows and panoramic photographs:
    • Imagination is a lightweight and simple DVD slide show maker for Linux and FreeBSD that’s very easy to use, offers a wide variety of transitions, supports background music, and much more. Available in the Debian and Fedora repositories, and probably many others.
    • Hugin is a program that allows you to assemble a mosaic of photographs into a complete, immersive panorama, stitch together any series of overlapping pictures, and much more. It’s cross-platform and easy to use.
  • Why Ham Radio? Richard talks about why you might wish to obtain an Amateur Radio License and how you can combine it with Linux, including:
    • Getting your ham license for our non ham listeners.
    • There are many modes of communication, including voice, Morse code, and many digital modes.
    • The ease of getting your license.
    • Why you should get your license.
    • How to get your license.
    • The Amateur Radio Relay League (ARRL) is a good source of information
    • Free practice tests are available at qrz.com
    • A list of certified Volunteer Examiner Coordinators is available at www.ncvec.org.
    • Test sessions can be found through the ARRL and many local radio clubs.
  • Russ describes Universal Plug ‘n’ Play devices (UPnP). Many new devices offer the ability to play media from UPnP servers. It makes sharing your media very convenient and easy, but can also be a security risk.

Feedback:

  • Pete, VE2XPL, sends a long email in response to episode 88, and covers such things as the Toonie, Alexandre Graham Bell, Brad Sucks, the wAVEgUIDES PodCast, SouthCARS, email addresses for LHS, and the MintCast.
  • Ted, WA0EIR, asked if there is a problem with the LHS mailing list as his attempts to post a message there “bounced”. Yes, the mailing lists have been broken, but they’re fixed now.
  • Larry Bushey of the Going Linux podcast says thanks for the great show, and admits they stole the LHS “badger” sound effect for use on their show. Episode 185 contains an example of their use of the Badger.
  • LHS was mentioned in a comment to a post at hak5.org.

Contact Info:

Music:

  • “You Are You” by Fall Walk Run from the album Throwing It All Away, courtesy of Jamendo.
  • “Flash Back” by MattMigma from the album Phoenix, courtesy of Jamendo.

PC power supplies for Amateur Radio equipment?

I’ve noticed a few spirited discussions regarding modifying computer power supplies for use with Amateur Radio equipment. On the surface it seems as though they supply the perfect solution: Inexpensive, high current, regulated 12V DC supplies for a fraction of the cost of specialized amateur equipment. Is it really is as straight forward as lopping off a molex connector and replacing it with an Anderson Powerpole?

By design PC power supplies are designed to output a fairly well regulated 3.3V & 5V to the PC motherboard and 12V to the motherboard, fans and hard-drive motors. Modern units are typically rated anywhere from 75W to 1200W which should be a measurement of the output power available from all the 3.3, 5 and 12 volts. Since this isn’t a lab grade power supply you can expect marketing hyperbole has perhaps inflated the power output figures.

Back when my job was to build PCs I had an issue with a server not being able to start its complete complement of disk drives. When I opened the case I found a 300W desktop supply board had been used in place of the 800W board … sometimes you don’t even get what you pay for!

Before you convert your first PC power supply there are two issues that may, or may not, cause a problem depending on your unit.

The first is load regulation or the ability of the power supply to maintain its rated voltage under load. If the output voltage drops too far your rig will shutdown, distort or fail to provide its rated output power.

The second issue is due to the high frequency switching circuits used in switch mode supplies. Depending on the individual power supply there can be adequate to no filtering to prevent radio frequency interference being broadcast to your receiver. Toroids on the input and output lines can help to reduce interference.

Because of construction differences between models and even between batch numbers for the same model you can never be certain how the power supply you purchase, or recycle, will perform. For the most part people’s experiences have been positive but I have heard of power supplies that were unusable because of RF interference or such poor load regulation that the 12V rail dropped to 11V under load.

Without a motherboard presenting a load and supplying the power-on signal there are a few changes that need to be made to the power supply. Modern power supplies will not enable the 12V output unless the power-on wire is grounded and a load should be placed on the 5V line to help with regulation. Additionally there is usually an adjustment that can be used to raise the voltage above 12V

The following links detail the steps required to convert a PC supply for use with amateur radio equipment. Whether this represents a good investment of your time will depend on your desire to do-it-yourself and the quality of the power supply you begin with. I’ve heard strong opinions either way but I’ll just say that, if luck favors you, you’ll save some money and learn a few new skills in this exercise.

Computer Power Supply Converted for Ham Use

CONVERTING COMPUTER POWER SUPPLIES (Advanced with theory)

Converting Computer Power Supplies to stabilized 13.8 V DC 20 A


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