【正文】 焊點表面要光滑、清潔，焊點表面應有良好光澤，不應有毛刺、空隙，無污垢，尤其是焊劑的有害殘留物質(zhì)，要選擇合適的焊料與焊劑。 因此，在系統(tǒng)上電前和 系統(tǒng)不能正常工作的時候，必須對系統(tǒng)進行相應的調(diào)試 。 2. 按照原理圖檢查極性電容等記性元件的正負極是否反接。 如果上電前排除錯誤，上電后系統(tǒng)仍然不能正常工作，則測試單片機和 ULN2021A是否能正常工作。 sbit a4=P1^4。 sbit a6=P1^6。 sbit b0=P2^0。 sbit b2=P2^2。 sbit b4=P2^4。 sbit b6=P2^6。 sbit c1=P3^1。 sbit c3=P3^3。 sbit c5=P3^5。 sbit c7=P3^7。 a3=0。 a5=0。 a7=0。 b1=0。 b3=0。 b5=0。 b7=0。 c1=0。 c3=0。 c5=0。 c7=0。將單片機嵌入工作電路，上電后使用萬用表測量單片機檢測各個 I/O 接口的高低電平是否和定義相符，相符則證明單片機工作正常。若輸入輸出電平都與測試程序相符，則ULN2021A 芯片工作正常。 第 6 章 結(jié) 論 由于數(shù)字電子技術(shù)的不斷發(fā)展， 已取得很大成就。在動力方面，由于傳統(tǒng)電機為模擬電子范疇，并不能直接與以計算機為代表的數(shù)字電子設(shè)備直接配合使用。但是步進電機作 為一種數(shù)字動力元件的出現(xiàn)，則大大的改善了此情況。 這對于對精度要求較高的現(xiàn)代機械控制有著重要意義。這就使得單片機驅(qū)動步進電機這一應用收到更廣泛的觀眾，本文在 此選擇較為簡單的單片機和步進電機及相應的芯片 ，組成簡單的步進電機驅(qū)動系統(tǒng)。研究其工作原理， 以及使用中的 具體 注意事項。 3． 搜集步進電機的驅(qū)動方案，對驅(qū)動方案進行比較，選取 合適的驅(qū)動方式。 5． 對 電 路各個部分的功能進行詳細的講解。下一步需要在電路上加獨立供電模塊以及電機暫停按鈕 以及轉(zhuǎn)向和速度的顯示 LED管 ， 將系統(tǒng)電路改進。 22 致 謝 值此畢業(yè)設(shè)計接近尾聲之際，謹向我的指導老師 —— XXX 老師表示衷心的感謝。 在本設(shè)計的制作過程中，由于牽扯到許多本人專業(yè)之外的知識，尤其是數(shù)字電子技術(shù)知識，使得本人 在 設(shè)計過程中著實遇到很多困難。在對待專業(yè)知識的態(tài)度上， X老師的博學和嚴謹給我留下了深刻的印象，X老師具備豐富的單片機開發(fā)經(jīng)驗和扎實的電子電路專業(yè)知識，這使我受益良多。在畢業(yè)設(shè)計過程中，我們 6人結(jié)為至交好友，我們互相幫助，相互配合，這保證了我們按時，順利地完成畢業(yè)設(shè)計。 在此，感謝答辯組老師的精心指導和寶貴的建議 ！ 最后，衷心感謝機電工程學院所有老師四年來對我的教導，感謝母校 —— XXXX 大學對我的栽培 。北京：清華大學出版社， 1996： 396397. [12]王伯林 .單片機系統(tǒng)設(shè)計的誤區(qū)與對策 [J].電子技術(shù)應用， [13] Kuo B C, Singh G. A DC type hybrid step motor for large power applications[J]. IEEE Trans on Ind, 1975, 12,365372 [14] Bryso A, Hu Yuehi. Applied optimal control. London: Hemishere Publishing Co,1975， 86290 ag an employment tribunal clai Emloyment tribunals sort out disagreements between employers and employees. You may need to make a claim to an employment tribunal if: you don39。t appealed against the disciplinary action your employer has taken against you. However, if you win your case, the tribunal may reduce any pensation awarded to you as a result of your failure to appeal. Remember that in most cases you must make an application to an employment tribunal within three months of the date when the event you are plaining about happened. If your application is received after this time limit, the tribunal will not usually accept i. If you are worried about how the time limits apply to you If you are being represented by a solicitor at the tribunal, they may ask you to sign an agreement where you pay their fee out of your pensation if you win the case. This is known as a damagesbased agreement. In England and Wales, your solicitor can39。s antiracism taskforce, is in London for the Football Association39。s Premier League match at Chelsea on Sunday. I am going to be at the match tomorrow and I have asked to meet Ya ya Toure, he told BBC Sport. For me it39。s 21 win. Michel Platini, president of European football39。s actions. CSKA said they were surprised and disappointed by Toure39。 May be back in the past, to oneself the paranoid weird belief disillusionment, these days, my mind has been very messy, in my mind constantly. Always feel oneself should go to do something, or write something. Twenty years of life trajectory deeply shallow, suddenly fe el something, do 到了尾聲?？傆X得自己似乎應該去做點什么，或者寫點什么。 The end of our life, and can meet many things really do? 而窮盡我們的一生，又能遇到多少事情是真正地非做不可？ During my childhood, think lucky money and new clothes are necessary for New Year, but as the advance of the age, will be more and more found that those things are optional。t really grow up, it seems is not so important。t want to give vent to out your inner voice can be in the high school children of the feelings in a period, but was eventually infarction when graduation party in the throat, later again stood on the pitch he has sweat profusely, looked at his thrown a basketball hoops, suddenly found hi mself has already can39。 instead of letting the world soften us, we let it drive us deeper into ourselves. We try to deflect the hurt and pain by pretending it doesn’t exist, but although we can try this all we want, in the end, we can’t hide from ourselves. We need to learn to open our hearts to the potentials of life and let the world soften ，我們常常會關(guān)上心門；世界不僅沒能慰藉我們，反倒使我們更加消沉。既然如此，何不嘗試打開心門，擁抱生活中的各種可能，讓世界感化我們呢？ Whenever we start to let our fears and seriousness get the best of us, we should take a step back and reevaluate our behavior. The items listed below are six ways you can open your heart more fully and ，我們應該退后一步，重新反思自己的言行。 Whenever a painful situation arises in your life, try to embrace it instead of running away or trying to mask the hurt. When the sadness strikes, take a deep breath and lean into it. When we run away from sadness that’s unfolding in our lives, it gets stronger and more real. We take an emotion that’s fleeting and make it a solid event, instead of something that passes through ，別再逃跑或隱藏痛苦，試著擁抱它吧；當悲傷來襲時，試著深呼吸，然后直面它。屏住呼吸，生活停滯；呼出呼吸，更多新奇與經(jīng)歷又將拉