Hysteresis in Engineering – Control Systems

Hysteresis can be used to filter signals so that the output reacts more slowly than it otherwise would, by taking recent history into account. For example, a thermostat controlling a heater may turn the heater on when the temperature drops below A degrees, but not turn it off until the temperature rises above B degrees (e.g., if one wishes to maintain a temperature of 20 °C, then one might set the thermostat to turn the furnace on when the temperature drops below 18 °C, and turn it off when the temperature exceeds 22 °C). This thermostat has hysteresis. Thus the on/off output of the thermostat to the heater when the temperature is between A and B depends on the history of the temperature. This prevents rapid switching on and off as the temperature drifts around the set point.

The thermostat is a system; the input is the temperature, and the output is the furnace state. The furnace is either off or on, with nothing in between. If the temperature is 21 °C, it is not possible to determine whether the furnace is on or off without knowing the history of the temperature.

How to remove add to wishlist or add to compare links on Opencart category and products page

You shall use the vQmod extension,


[[ or ]]

You must edit 2 files under your template folder (catalog/view/theme/your template name/template/product/):

1. product.tpl
2. category.tpl

For both files, edit by commenting codes as follows:

<div><!–<a onclick=”addToWishList(‘<?php echo $product_id; ?>’);”><?php echo $button_wishlist; ?></a>–></div>
<div><!–<a onclick=”addToCompare(‘<?php echo $product_id; ?>’);”><?php echo $button_compare; ?></a>–></div>

Result: No wishlist nor Compare and yes, no more null error.



How to Install vQmod on Opencart

Download the latest version from http://code.google.com/p/vqmod

Using FTP, upload the “vqmod” folder from the zip to the root of your opencart store.

ensure vqmod folder and the vqmod/vqcache folders are writable (either 755 or 777). Also check index.php and admin/index.php are writable.

Now install vQmod by visiting the url, http://www.yoursite.com/vqmod/install

You should get a success message.