A Wall St. sign is seen outside the entrance of NYSE Thomson Reuters By Tanya Agrawal

(Reuters) - U.S. stock index futures fell on Wednesday as Chinese stocks had another roller coaster ride and as investors await the minutes from last month's Federal Reserve meeting for clues on when interest rates will be increased.

* While the health of the U.S. economy appears to be stabilizing, the effect of the yuan devaluation and other macro factors are playing on investor's minds. The Fed minutes will be released at 2 p.m. ET.

* Economists believe the Fed will probably raise rates twice this year, with the first hike coming in September. Investors are still not fully convinced of a September hike, but most are betting a rate hike will occur by the end of year.

* Chinese stocks reversed sharp declines and ended higher after the central bank injected more funds into the financial system for a second day in a bid to calm panicky markets.

* The People's Bank of China devalued the yuan last week, triggering an avalanche of selling by investors globally who feared Beijing wanted to engineer a much sharper decline to support weak exports.

* The Chinese market gyrations kept commodity prices under pressure, with oil and copper near six-year lows.

* Other data due Wednesday is expected to show consumer prices rose 0.2 percent in July, less than the 0.3 percent rise in June. The Consumer Price Index data is due at 8:30 a.m. ET.

* Lowe's shares fell 1.6 percent to $71.85 in premarket trading after the No.2 U.S. home improvement chain's quarterly profit missed expectations.

* Yum Brands rose 1.5 percent to $85.50, a day after the owner of the KFC and Pizza Hut chains announced new leadership for its China division as activist investors lobby the company to spin off that business.

* Staples fell 1.6 percent to $13.93 after the office supplies retailer reported quarterly revenue slightly below analysts' estimates, hurt by a stronger dollar.

Futures snapshot at 7:07 a.m. ET:

* S&P 500 e-minis were down 5.25 points, or 0.25 percent, with 143,877 contracts traded.

* Nasdaq 100 e-minis were down 11 points, or 0.24 percent, on volume of 23,476 contracts.

* Dow e-minis <1YMc1> were down 57 points, or 0.33 percent, with 22,069 contracts changing hands.

(Reporting by Tanya Agrawal in Bengaluru; Editing by Savio D'Souza)