How to create a Bollinger Bands Expert Advisor

The video begins with the creation of a Bollinger Bands standalone Expert Advisor that will trade the Bollinger Band signals. A sell trade has already been made, and the tutorial aims to explain how this can be done in MQL5 (0:00).
The Metaeditor window is opened, and a new Expert Advisor is created from the template. This new Expert Advisor is named “SimpleBollingerBandsStandalone” (8:00).
The tutorial then proceeds to delete everything above the “OnTick” function and removes the two command lines. The Trade.mqh file is included to create a “CTrade” instance called “trade”, which will be used later to open a position (14:00).
An empty string called “entry” is created, and the Ask price and the Bid price are obtained using “SymbolInfoDouble” for the current symbol. The “NormalizeDouble” function in combination with “_Digits” is used to get the number of digits for the current symbol of the current chart (22:00).
An array for the prices called “PriceInfo” is created in the “MqlRates” format. The price array is sorted from the current candidate downwards using “ArraySetAsSeries” (28:00).
The “CopyRates” function is used to fill the “PriceInfo” array with price data for the current symbol and the currently selected period on the chart from the current candle 0 for 3 candles (35:00).
Arrays for several prices for the upper and lower band of the Bollinger Bands are created. When the price breaks out and re-enters into the Bollinger Bands, it would be a signal. A buy signal occurs when it does it from below, and a sell signal occurs when it does it from above (39:00).
The Bollinger Bands are defined by using the built-in “iBands” definition for the current symbol on the chart and the currently selected period. The period of 20 candles, a shift value of 0, and the deviation value of 2 are used, and the calculation is based on the close price (47:00).
The “CopyBuffer” function is used to copy the “PriceInfo” into the Bollinger Bands definition array. Buffer 1 and buffer 2 are used to calculate the upper and the lower band from the current candle 0 for 3 candles (55:00).
The Expert Advisor for the current candle is calculated, and the values for the upper and lower band are obtained. To calculate a crossover, the Expert Advisor for the candle before (candle 1) is also calculated (60:00).
A check is made to see if there is a re-entry from below. This would be true if the close price for candle 0 is above the lower band value and if the close price for the candle before was below the last lower band value. In this case, a buy entry is made (66:00).
A check is also made to see if there is a re-entry from above. This would happen if the current price is below the upper band value and if the price for candle 1 was above the last upper band value. In this case, a sell entry is made (72:00).
If the entry equals sell and there are no open positions, a sell of 10 micro lot is made. If the entry equals buy and there are no open positions, a buy of 10 micro lot is made (77:00).
The “Comment” function is used to output the words “Entry Signal” followed by the calculated entry directly on the chart (85:00).
The tutorial ends with the compilation of the code and the return to Metatrader. The “SimpleBollingerBandsStandalone.ex5” file is selected in the Strategy Tester, and the visualization option is marked. The test is then started, and the Expert Advisor is shown at work (94:00).
The video concludes with the explanation of how to automate the Bollinger Bands signal with MQL5 and create a simple standalone Expert Advisor that is actually going to trade with a few lines of MQL5 code (103:00).

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