Chipkin Automation Systems - Articles

How to add a MediaWiki article to a category

xcosminel — Fri, 03 Jul 2009 23:23:58 +0000

Assigining your articles to corresponding categories is very important for helping your visitors navigate your MediaWiki site with ease. Thankfully, MediaWiki comes with an included system for handling categories.

To add an article to a category:
Simply edit the article you want to add to the category, and add the following line at the end of the contents:

[[Category: Nameofcategory]] (where Nameofcategory is your category name)

It doesn’t matter if the category does not exist or was never used before. MediaWiki will create a new page for each category containing all of the articles that were added to it.

Pasting from Word into Wordpress (Paste from Word)

xcosminel — Fri, 26 Jun 2009 22:02:31 +0000

There is a common issue when posting from Word into the Wordpress editor which causes problems when trying to view the article using the Internet Explorer browser (it simply won’t display).

The reason behind this is because Word uses some unstandardized tags for its formatting, and those tags are not recognized by IE.

Quick Fix (and a really bad way to do it):

To quickly fix an article where the issue occurs, follow these steps:

Go back and edit the article.
Switch from Visual view to HTML view.
Remove any text occuring before the tag, including the tag itself.
Switch back to Visual view and see if the article was fixed.
Update the article.

Currently a few different plugins for WordPress are being developed which should stop the issue from occuring. I haven’t found a working one yet. If anyone does please comment away!

Node Offline Responses

skapoor — Mon, 01 Jun 2009 12:52:36 +0000

When a Client Node on the FieldServer goes offline the corresponding data objects on the FieldServer are also marked offline. If a client polls a virtual FieldServer node for this particular data, an offline response will be returned by the FieldServer. If the client then requests the FieldServer to identify itself, a valid response will be provided in spite of the data being offline. This results in status toggle, with the Server side Client receiving no replies to data requests and marking the Node offline and then again marking the node online after a successful identification poll, then again receiving no replies to data requests and marking the node offline and so on.

The Server Node must therefore be capable of deciding the nature of its response based on the status of relevant Client Nodes. This can be accomplished using responsible Map Descriptors (RDBC, WRBX, and WRBC). In case no acknowledgement of these functions is received, the device is identified as offline and a flag is placed at the data array offset. The virtual FieldServer can be configured using the Offline_Method option to respond to identification requests in one of the following ways:

Ignore_Clients/No Setting (default) – The kernel ignores the status of Client side Nodes and uses only the online/offline status of relevant data objects to decide on the type of response.
Any_Offline – If any relevant Client Node is offline the Server Node will respond with a node offline message as defined by the Server protocol. This option is available for selected drivers only.
All_Offline – If all relevant Client Nodes are offline the Server Node will respond with a node offline message as defined by the Server protocol. This option is available for selected drivers only.
Always_Respond – A response with data currently in the FieldServer is always sent, without considering the online/offline status of the relevant Client Nodes. This option is available for all drivers.

Offline Server Nodes are treated differently by different protocols. Some protocols will have an explicit offline response, while others will simply not respond.

If configured, the node offline response will take priority over the data offline response.<-->

Timing Parameters

skapoor — Mon, 01 Jun 2009 12:46:13 +0000

Normally a FieldServer sends a poll request to a Server device and that device gives a response back to the FieldServer.

Following are the timing parameters considered important in the fieldserver’s operation:

Scan_interval: It is the amount of time between successive poll requests. Its default value is 2 seconds and it belongs to Map descriptors, nodes and connections.

Poll_delay: It is the time between receiving a response from a server device and the next poll request. Its default value is 0.05 seconds and it belongs to Connections only.

Timeout: If the FieldServer sends a poll request, and the Server device does not send a response, it is considered a timeout. The time for which the FieldServer waits before declaring a timeout can be adjusted by the timeout parameter. Its default value is 2 seconds and it belongs to Map descriptors, nodes and connections.

ic_timeout: This parameter monitors the time between characters in a response. If the time exceeds the ic_timeout, the response is discarded and is considered a timeout. Its default value is 0.5 seconds and it belongs to Map descriptors, nodes and connections.

Retries: If a timeout occurs, then the FieldServer will retry the poll request a few more times. Number of times tried is specified by the retries parameter. Its default value is 3 times and belongs to nodes only.

Retry_interval: The interval between retries is specified by the retry_interval. The Fieldserver will send poll requests at the end of each retry_interval. Once the specified numbers of retries have been sent, the FieldServer will mark the node offline. Its default value is 10 seconds and belongs to nodes only.

Recovery_interval: Once a node has been marked offline, it will wait for a period specified by recovery_interval before sending another poll request. Its default value is 30 seconds and it belongs to nodes only.

Probation_delay: Once the communications have been re-established, the FieldServer will wait for a period called probation_delay, before marking the node as online. Its default value is 1 minute and it belongs to nodes only.

Tags v/s Categories

skapoor — Mon, 01 Jun 2009 12:36:37 +0000

Earlier, WordPress.com used only categories and no tags. A tag is a new breed of search engine optimization i.e. SEO. Tags are fundamentally keywords for each page or article created by us. It is a non-hierarchical keyword or term assigned to a piece of information such as an internet bookmark, digital image, or computer file. This type of metadata helps depict an item and facilitates it to be found again by browsing or searching. Tags are chosen easily and personally by the item’s creator or by its viewer, depending on the system. Tags are “free-form” words means there is no formal restriction on tags we attach.

Long tag lists should be generally avoided. Tag pages are somewhat like category pages. We can assign related posts the same tag, and then all those posts appear on the same tag page. During the design stages of the site, make a list on a piece of paper of all the tags we want to use on our site. These will be the most important keywords for the niche, but they should be keywords that are different to the categories which we have setup for the site. Tags can be considered as additional pages that Wordpress will create offering us a secondary way of filing our posts.

Although, usage of tags made broad grouping of post topics possible yet to describe a post in more specific terms, more categories are needed. A category is an exclusively defined division in a system of classification. A system of classification here refers to a highly structured, possibly hierarchical system. For example, to borrow from the classification system for living things, we have a tree like “Animals -> Vertebrates -> Mammals -> Horses”. Any of these terms can be considered to be a category, and they fall into a strict structure.

The basic difference between categories and tags is that categories are structured and tags are unstructured. Categories organize, hierarchically. Tags need not. Tags provide meta-information, Categories need not. Tags cross-connect, Categories do not. <–>

FieldServer 485 Connection Diagram to Isolator ICD102A (Black Box)

skapoor — Mon, 25 May 2009 09:06:07 +0000

This diagram shows how to connect a FieldServer FS20 series to an ICD102A optical isolator using a 2-wire RS 485 connection. FieldServer’s only support 2 wire connections.

Datasheet for the Black Box RS485 Isolator/Repeater can be found here: Blackbox Network Services

Google Page Rank

skapoor — Mon, 25 May 2009 05:24:37 +0000

PageRank is a link analysis algorithm used by the Google Internet search engine that assigns a numerical weighting to each element of a hyperlinked set of documents, such as the World Wide Web. The purpose behind this is to measure the relative importance of the element within the set. It is a probability distribution check which represents the possibility that a person randomly clicking on links will arrive at any particular page.

Google Adwords

skapoor — Mon, 25 May 2009 05:11:08 +0000

AdWords is Google’s flagship advertising product and main source of revenue. AdWords offers pay-per-click (PPC) advertising, and site-targeted advertising for both text and banner ads. The AdWords program consists of local, national, and international distribution. Google’s text advertisements are short and contain one title line and two content text lines whereas Image ads can be one of several different Interactive Advertising Bureau (IAB) standard sizes. Main competitors of Google AdWords are Yahoo! Search Marketing and Microsoft adCenter. Advertisers specify the words that should trigger their ads and the maximum amount they are willing to pay per click. When a user searches Google’s search engine on www.google.com or the relevant local/national google server ads for relevant words are shown as “sponsored links” on the right side of the screen, and sometimes above the main search results. These ads are also known as creatives by Google.

The ordering of the paid-for listings depends on other advertiser’s bids and the “quality score” of all ads shown for a given search. The quality score is calculated by historical click-through rates, relevance of an advertiser’s ad text and keywords, an advertiser’s account history, and other relevance factors as determined by Google. The quality score is also used by Google to set the minimum bids for an advertiser’s keywords. The minimum bid reflects on the quality of the landing page also, which includes the relevancy and originality of content, navigability, and transparency into the nature of the business.

All AdWords ads are eligible to be shown on www.google.com. Another option available for advertisers is of enabling their ads to show on Google’s partner networks. The “search network” includes AOL search, Ask.com, and Netscape. Like www.google.com, these search engines show AdWords ads in response to user searches. The “content network” shows AdWords ads on sites that are not search engines. These content network sites are those that use AdSense, the other side of the Google advertising model. AdSense is used by website owners who want to earn money by displaying ads on their websites.

RS485 Networks – Multiple Protocols

pchipkin — Fri, 15 May 2009 21:52:19 +0000

RS485 defines the physical layer of the network. You may use it as you want. However, since the trunk is shared it is important that no two (or more) devices talk at the same time. If they do this will produce collisions and the corruption of both messages.

The following applies for both half and full duplex RS485.

You can have any number of protocols on the same 485 trunk provided that two or more devices do not talk at the same time.
The consequences of this statement are
1. You can only use more than one protocol if they are poll/response type protocols like Modbus Rtu or Rockwell DF1.
2. If you have a token passing protocol (such as Bacnet mstp) you cannot use another protocol on the same trunk
3. Only one device can be the master for the multiple protocols. The reason is that the master decides when to poll and how long to wait for a response.

Thus, If you have full control over one rs485 port you could use that port to send a poll using protocol#1, wait for a response and then send a poll using protocol#2. If you do not have full control (ie. You are letting two applications which are not co-ordinated share the port) then you cannot run two protocols.

Get to know your Power Meter – What is Real, Apparent and Reactive Power

xcosminel — Tue, 28 Apr 2009 00:12:11 +0000

First – a simple question

Right or Wrong? Power = Voltage x Current

That statement is correct for DC systems but there are two major complications for AC systems.

The value of current and voltage keeps changing. Which value do you use ?
The voltage and the current may not be in phase. Multiplying the current and the voltage when they are not in phase requires and adjustment to compensate for the phase. It is this phase shift that forces us to define Real, Apparent and Reactive Power.
This phase shift occurs when a power source feeds an inductive or capacitve load”. Most loads are either inductive (motors) or resistive (heaters) and therefore the phase shift is typically in one direction.
- A motor has a winding. A wound conductor essentially defines an inductor. Thus the winding presents the resistance of the wound wire and the inductance resulting from the winding.

RMS or Effective Value

Peak values in the alternating voltage or current curves only lasts a short instant. They are not really representative of the ability of the voltage and current to do work and thus they are not used in Power Calculations.Scientists use a statistical method to define the effective values. It is called the RMS or Root-Mean-Square values. The result of the definition is that:Veff / rms = 0.707 x Vpeak

The same applies to current too.

TIP: You can reasonably assume that all the Voltages and Currents reported by a Power Meter are reported as RMS or Effective values unless otherwise indicated.

TIP: Most multi meters report RMS values

Apparent Power

Apparent Power is the power delivered by a power source to a load like a motor. In almost all real world situations that use AC, you need to supply more power (Apparent Power) to a device than it will do work (Real Power).The (vector) difference between the two represents the work done to overcome the inductive and capacitive effects of the load.Apparent Power is measured in units of VA – Volt-amperes. These are actually Watts but we use the new unit name to reduce confusion. Thus when you see VA on a data sheet you can reasonably conclude that they are talking about Apparent Power.

Apparent Power is calculated:

S(Common symbol for Apparent Power) = Veff / rms x Ieff / rms – Single Phase Calc

Power Factor and Phase

Power Factor is calculated: PF = Cosine ( phase angle in radians)Power factor has no engineering units.The value of PF ranges from -1 to 0 to 1 (lagging – none – leading)

Loads that only present a resistive load (no capacitance or inductance) have a PF of 1.

Inductive Loads

Current phase lags the VoltageTypical – Transformers and motors (wound conductors)

Capacitive Loads

Current phase leads the VoltageTypical – Buried Cables, capacitor banksThere is nothing ‘wrong’ with having a power factor that isn’t 1.0.

Real Power and Reactive Power

Think of Real Power as useful power – a measure of how much work is being done.The units of Real Power are Watts.Real Power is calculated : P(Real) = S(Apparent Power) x pf

Reactive Power is the (vector) difference between Apparent Power and Real Power. The energy used to produce the Reactive Power is stored in the magnetic/electrical field of the Inductive Load. In the case of the capacitive load the magnetic/electrical field of the Inductive Load produces the Reactive Power. Reactive Power cannot be harnessed to do useful work.

Reactive Power is identified by the symbol : Q

The engineering units of Reactive Power are VAR – Volt-amperes Reactive. These are also Watts but we use VAR so that we know we are talking about Reactive Power.

Diagram: RMS measurement

Diagram: Leading / Lagging

THD – Total harmonic Distortion (also called Distortion)

In simple terms THD is a measure of distortion reported as %. If a device (any active device but think of rectifiers, variable speed drives … as practical examples) is given a sine wave as in input the output is never a faithful 100% reproduction of the input. A series of harmonics of the original wave distort the original wave form. The THD % is an attempt to ‘numberize’ the degree of distortion to allow for comparison. The % number is somewhat controversial because some harmonics are more important than others and there is no weighting.THD(%) = 100 * SQRT[(V22 + V32 + V42 + ... + Vn2)] / VtWhere V2, V3 are the RMS values of each voltage harmonic and Vt is the total RMS output voltage.

Sag / Swell or Dip / Surge

Duration is 0.5 cycle and greater. Voltage sags are the most common power disturbance. Voltage sags can arrive from the utility. In most cases, sags are generated inside a building. For example, in residential wiring, the most common cause of voltage sags is the starting current drawn by refrigerator and air conditioning motors.Sags do not generally disturb incandescent or fluorescent lighting. motors, or heaters. However, some electronic equipment lacks sufficient internal energy storage and, therefore, cannot ride through sags in the supply voltage. Equipment may be able to ride through very brief, deep sags, or it may be able to ride through longer but shallower sags.

Under / Over Voltage

Over Voltage is an increase in effective voltage to more than 110% for longer than one minute. Under Voltage is a decrease in effective voltage to less than 90% for longer than one minute. Take care with this definition because it tends to change from vendor to vendor.

Transient Voltages / Spikes / Surges

Refers to short duration (less than 1 cycle) events. Low frequency transients are often called “capacitor switching transients”. High frequency transients are often called impulses, spikes, or surges. They can be caused when a discharged power-factor-correction capacitor is switched on across the line.High frequency transients are caused by lightning, and by inductive loads turning off. Typical rise times are on the order of a microsecond; typical decay times are on the order of a tens to hundreds of microseconds. Often, the decay will be an exponential damped ringing waveform, with a frequency of approximately 100 kHz.Extremely fast transients, or EFT’s, have rise and fall times in the nanosecond region. They are caused by arcing faults, such as bad brushes in motors, and are rapidly damped out by even a few meters of distribution wiring. Standard line filters, included on almost all electronic equipment, remove EFT’s.